BZ-1869593: Recommend against modifying the default roles

Author: bergerhoffer

modules/rbac-overview.adoc

@@ -78,9 +78,12 @@ For example:
 [id="default-roles_{context}"]
 == Default cluster roles
 
-{product-title} includes a set of default cluster roles that you can bind to
-users and groups cluster-wide or locally. You can manually modify the default
-cluster roles, if required.
+{product-title} includes a set of default cluster roles that you can bind to users and groups cluster-wide or locally.
+
+[IMPORTANT]
+====
+It is not recommended to manually modify the default cluster roles. Modifications to these system roles can prevent a cluster from functioning properly.
+====
 
 [cols="1,4",options="header"]
 |===