Instantiate different rooms from the client without defining each room id

Is there a way to instantiate different rooms from the client without defining each room id? What I want to achieve is for the players to be able to create their own rooms. I know that the client.joinOrCreate would create a new room only when the room id is defined on the server like this:
gameServer.define('roomId', Room);

How can I create different rooms from the client-side without having to define each id? I want the client to be able to create rooms with any id without defining that id explicitly in the server.