Sorry, I posted before I finished the mail...:)
At point 2..
lobbyRoomInstance.addHandler(add your session event handler which listens for ROOM_LIST event).
In the onEvent method of this handler you can write code like
getSession().send(new NetworkEvent(data)) where data is nothing but a list of string of room names that are part of this special LobbyRoom.
3. At client side, you need to send this ROOM_LIST event to server to get back the list of rooms that this LobbyRoom has.
I think this is a common requirement that you are asking. So I will try to provide a default implementation for this in near future. Little bit busy now, but hopefully in couple of weeks.
Thanks,
Abraham.