What I meant was, that if the room is members-only, you could display all the members in the “room roster”, even if all of them are in fact offline. Members are persistent and affiliated to the room.
I’ve done it like that:
First, request all members, then request all admins, then request all owners, then display all together in a room roster as offline.
Requesting works like that:
As soon as a presence is received from one of the members, switch him to online. This way you have online and offline users displayed in the same room roster.
Actually I’ve made every member as an owner, so that every member could modify the members list and invite new members. I am also not sure, if mere members are allowed to retrieve the members list.
You probably have to write your own client software, because most existing software (also like Adium) uses just the room occupants (instead of members) to display them in the room roster. Occupants are always online and disappear from the room when they go offline.