From the doc :
Join the first available room with the given game, instance and first room name. The player must be connected and logged in to the signalling server. The first player to join a room becomes the host. Be sure to use a unique name for the Game. For example if "myroom" is full, it will try "myroom2", "myroom3", etc. This effectively arranges all joining peers in to games of a particular size. If the room is locked when full, then late-joiners are not allowed; if left unlocked and a peer leaves after the game starts, a newly joining peer may be added back to the game to top it up to the Max peers again. Upon joining, On joined room triggers.
I'm a bit confused:
1) Why must i specify the room name if the engine already looking for an available room automatically?
2) I wonder also how to manage several rooms rather than using a same room name like what you done in the tutorial? database is needed in that case?
3) Can Auto-join room create new rooms if it can't find any available room ?