If you're not currently in a room, the `Create a Room` and `Join a Room` links show at https://secure.phabricator.com/conpherence/
On my install, once a user is in a room, they can only find the room creation workflow from https://secure.phabricator.com/conpherence/search/ (which for some reason changes the top right from `New Message` to `New Room`)