I want to get roomlist so the player can choose the room; I don't see any function in their documentation.
As far as I know, rooms don't work like that. You have 2 ways of creating and joining rooms. Auto-match: All players creates a room automatically and Google merges them according to the settings set previously, like bit-mask, minimum players to start, and so on Invitations: A room is created by the host and the others join it when accepting the invitation.