diff --git a/py-polars/polars/expr/expr.py b/py-polars/polars/expr/expr.py
index f4012256ed13..dd02a58656fc 100644
--- a/py-polars/polars/expr/expr.py
+++ b/py-polars/polars/expr/expr.py
@@ -4684,22 +4684,25 @@ def rolling_min(
         this window will (optionally) be multiplied with the weights given by the
         `weight` vector. The resulting values will be aggregated to their sum.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"`
+        means the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
         window_size
-            The length of the window. Can be a fixed integer size, or a dynamic temporal
-            size indicated by a timedelta or the following string language:
+            The length of the window. Can be a fixed integer size, or a dynamic
+            temporal size indicated by a timedelta or the following string language:
 
             - 1ns   (1 nanosecond)
             - 1us   (1 microsecond)
@@ -4733,7 +4736,8 @@ def rolling_min(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
 
         Warnings
         --------
@@ -4795,16 +4799,19 @@ def rolling_max(
         this window will (optionally) be multiplied with the weights given by the
         `weight` vector. The resulting values will be aggregated to their sum.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"`
+        means the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -4844,7 +4851,8 @@ def rolling_max(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
 
         Warnings
         --------
@@ -4906,16 +4914,19 @@ def rolling_mean(
         this window will (optionally) be multiplied with the weights given by the
         `weight` vector. The resulting values will be aggregated to their sum.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"`
+        means the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -4955,7 +4966,8 @@ def rolling_mean(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
 
         Warnings
         --------
@@ -5017,16 +5029,19 @@ def rolling_sum(
         this window will (optionally) be multiplied with the weights given by the
         `weight` vector. The resulting values will be aggregated to their sum.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"`
+        means the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -5066,7 +5081,8 @@ def rolling_sum(
             set the column that will be used to determine the windows. This column must
             of dtype `{Date, Datetime}`
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
 
         Warnings
         --------
@@ -5129,16 +5145,19 @@ def rolling_std(
         this window will (optionally) be multiplied with the weights given by the
         `weight` vector. The resulting values will be aggregated to their sum.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"` means
+        the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -5178,7 +5197,8 @@ def rolling_std(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
         ddof
             "Delta Degrees of Freedom": The divisor for a length N window is N - ddof
 
@@ -5243,16 +5263,19 @@ def rolling_var(
         this window will (optionally) be multiplied with the weights given by the
         `weight` vector. The resulting values will be aggregated to their sum.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"`
+        means the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -5292,7 +5315,8 @@ def rolling_var(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
         ddof
             "Delta Degrees of Freedom": The divisor for a length N window is N - ddof
 
@@ -5358,16 +5382,19 @@ def rolling_median(
         """
         Compute a rolling median.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"` means
+        the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -5407,7 +5434,8 @@ def rolling_median(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
 
         Warnings
         --------
@@ -5467,16 +5495,19 @@ def rolling_quantile(
         """
         Compute a rolling quantile.
 
-        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then by default the
-        windows will be:
+        If ``by`` has not been specified (the default), the window at a given row will
+        include the row itself, and the `window_size - 1` elements before it.
+
+        If you pass a ``by`` column ``<t_0, t_1, ..., t_2>``, then `closed="left"`
+        means the windows will be:
 
             - [t_0 - window_size, t_0)
             - [t_1 - window_size, t_1)
             - ...
             - [t_n - window_size, t_n)
 
-        Otherwise, the window at a given row will include the row itself, and the
-        `window_size - 1` elements before it.
+        With `closed="right"`, the left endpoint is not included and the right
+        endpoint is included.
 
         Parameters
         ----------
@@ -5485,8 +5516,8 @@ def rolling_quantile(
         interpolation : {'nearest', 'higher', 'lower', 'midpoint', 'linear'}
             Interpolation method.
         window_size
-            The length of the window. Can be a fixed integer size, or a dynamic temporal
-            size indicated by a timedelta or the following string language:
+            The length of the window. Can be a fixed integer size, or a dynamic
+            temporal size indicated by a timedelta or the following string language:
 
             - 1ns   (1 nanosecond)
             - 1us   (1 microsecond)
@@ -5508,8 +5539,8 @@ def rolling_quantile(
             If a timedelta or the dynamic string language is used, the `by`
             and `closed` arguments must also be set.
         weights
-            An optional slice with the same length as the window that will be multiplied
-            elementwise with the values in the window.
+            An optional slice with the same length as the window that will be
+            multiplied elementwise with the values in the window.
         min_periods
             The number of values in the window that should be non-null before computing
             a result. If None, it will be set equal to window size.
@@ -5520,7 +5551,8 @@ def rolling_quantile(
             set the column that will be used to determine the windows. This column must
             be of dtype Datetime.
         closed : {'left', 'right', 'both', 'none'}
-            Define which sides of the temporal interval are closed (inclusive).
+            Define which sides of the temporal interval are closed (inclusive); only
+            applicable if `by` has been set.
 
         Warnings
         --------