That's impossible. First off, you can't configure rooms in WR like a dedicated server, so you're forced to stick to K2's rules. Second, you don't join rooms directly. You have to send a request to the K2 server, asking if you can make a connection with the other players inside a room before you can join I think.
So yeah, no dice =\ This kind of thing works for some games, but WR isn't one of them.