It would be nice to Group permission Chat Rooms.

Unless I've misunderstood what you mean, you can already set Group permissions for Chat.

ACP -> System -> Applications -> expand "Chat" category on the right -> click the padlock (permissions) icon to the right of the Chat module -> select the Groups you want able to use Chat, and save the popup.

If that's not what you meant, however, can you please clarify?

I will ask the team member who requested this..

I'm going to assume with the rest of the context it's supposed to be group chats, like room 1 has 3 people in it and room 2 has 7 people.