After "On Logged In" triggers, you can "Request Room List"
In the "On Room List" event, you can use the room list expressions:
After On room list, the number of rooms in the received list.
After On room list, retrieve information for a room at an index in the received list. The state can be one of "available", "locked" or "full".
For example, to list all available room names in a text object, you could put in a subevent:
Repeat ListRoomCount times - TextObject - Append "ListRoomName(loopindex)&newline"
Or you can add all the rooms to a list object, so that users can select a room to join.