We don't have upper bound limits for users and rooms:
- users: we can handle as many users as you are willing to pay for
Well, not exactly, but almost. The two "bottlenecks" limiting the number of users are metered total user connection time and the traffic/client cpu load generated by maintaining the "roster" (this second factor can be reduced enabling anonymous presence, a new feature that we introduced with the last SDK)
- rooms: we don't limit the number of rooms you can create. When you create a room we just allocate a few static data structures (file-like database rows) so the physical limit would be our data repository size. Note that if you create thousands of rooms you'll have a very hard time trying to manage them via DevPortal and/or service API (all rooms for the account are kept in a single "folder" so listing that folder will be a very slow operation) but you can keep the list in your database.