I'd been kicked from a room once before for no reason, went to rejoin to ask why and I got in perfectly fine (before promptly being kicked again and receiving a message saying "GTFO"
So it would seem the room doesn't need to be closed for you to be able to join again, it's just blocking that results in that. Unless I just had an "odd one out" situation, since that's the only instance of being kicked out I've experienced