When you need to get someone's attention in the restricted persistent chat room, you can mention them. They'll get notified in the My Mentions section of the persistent chat room filters. You'll still get notifications when someone mentions you even if you've muted that persistent chat room.
Use @ , enter the person's name, and select it from the search results.
In Cisco Jabber for Windows client, you can use @ symbol to search for people that are available in the Cisco Jabber directory, but not in any particular room. When you search for those people they don't receive any notification.