Different XMPP servers have different rules about who can create rooms. I made the assumption that most servers allow public creation of rooms, which has been the case in my own experience.
In those cases, creating a room is simply the act of joining a room that doesn't yet exist.
It's possible to configure a server to not allow such room creation. They may require the room to be configured or for only certain users to create rooms.
There are two ways to diagnose this:
1) Watch the traffic from the server, and look at what error you are getting instead of the expected response.
2) Attempt to use a real XMPP client to create a room on the same server and see if it succeeds. Note that in the case that a room requires configuration, the client may do this silently for you.
I didn't put all this into the sample apps in order to keep them simple.
Let me know what you find, and I'll do what I can to help you figure it out.