[DOCS] Note index rollover is not automatically monitored (#40464)

Author: jrodewig

docs/reference/indices/rollover-index.asciidoc

@@ -1,8 +1,14 @@
 [[indices-rollover-index]]
 == Rollover Index
 
-The rollover index API rolls an alias over to a new index when the existing
-index is considered to be too large or too old.
+The rollover index API rolls an <<indices-aliases, alias>> to a new index when
+the existing index meets a condition you provide. You can use this API to retire
+an index that becomes too large or too old.
+
+NOTE: To roll over an index, a condition must be met *when you call the API*.
+{es} does not monitor the index after you receive an API response. To
+automatically roll over indices when a condition is met, you can use {es}'s
+<<index-lifecycle-management, index lifecycle management (ILM) policies>>.
 
 The API accepts a single alias name and a list of `conditions`. The alias must point to a write index for
 a Rollover request to be valid. There are two ways this can be achieved, and depending on the configuration, the