How room work on socket.io?

I've read socket.io document but its poor. I have few questions like this:

1. How can i define property for one room like: room.isPlaying, room.createdDate ...
2. Where the rooms data store? In the memory? Will memory be auto release after noone left on that room? Because if there are too much empty room created will consume server memory
3. Now, i'm using object to store room data and handle the empty room: delete when no-one left. Does it the same with using default socket.io room?

via TomSawyer