Anyone with knowledge of the room UUID can listen to the conversation, even though the presence of the eavesdropper may (or may not) show up in the connected peers' counter. It is of essence to share such UUIDs over a secure channel, or the communication security will be compromised trivially.
It is mentioned in the README the relevance of government level threat actors and email, SMS, Discord, among the possible mediums over which the UUIDs can be shared. Of course this leaves Chitchatter open to be attacked by governments and network operators, who do have access to the phone network(s), email servers, and other platforms involved. It would be best to prefer other out-of-bound channels, or come up with one-time UUIDs generators able to resynchronise and shared among the peers.