Is this really much different to being able to create an open room but restrict certain users to readonly access.
In fact, wouldn't this be a friendlier approach for new members; where access is granted straight away but can be suspended for "disruptive behaviour".
When you create a chat room, you will have the option of specifying a lockword or not.
If you specify a lockword, anyone trying to join your room will be asked to specify the lockword before they are allowed to enter.
There is only the complete suspension from chat that is available for moderators.
Who becomes chat owner is often a pretty random choice, so I'd be wary to give chat owners more powers.
Moderators can see deleted messages, so the deletion won't stop them from investigating the situation.
It keeps a fat red count on their gravatar of how many messages have been removed (so it can be tracked). Flagging the user hasn't worked so far, although he is currently under suspension for claiming to be 13 (which he probably isn't).
Moderators have been either selected by SE staff or elected by the community of an SE site, so there is a bit more screening than for room owners.
I'd also like to recommend the "block user" function, if someone is annoying you this feature allows you to completely ignore all their posts.
They are differentiated from room admins by having their nickname appear in red in addition to having the @ sign.
If you abuse the admin privileges, your group and your ability to create future groups will be removed, so please make sure you understand what is required in the admin role.