Regardless of authentication types, conference participants fall into one of two user role groups during a conference: presenters or attendees. Office Communications Server 2007 R2 keeps track of user roles for each conference participant. These user roles are used to authorize users to have access to different in-conference functionalities, which are summarized in the following list.

All authenticated enterprise users and federated users can join a conference as pre-set presenters. Anonymous users can join a conference only as attendees. However, once they have joined, anonymous users can be promoted to presenter by any existing presenter in a conference. In addition, there is an implicit role of organizer who creates a conference, whether impromptu or by scheduling.

Every Office Communications Server 2007 R2 conference is associated with an organizer. An organizer must be an authenticated enterprise user. If a user is deleted from the enterprise Active Directory, all Office Communications Server 2007 R2 conferences the user organizes are also removed from the conferencing database on the back-end database. The content that was created in conferences that were organized by such an organizer is also removed through a content expiration feature. An organizer is by definition also a presenter and determines who else can be a presenter. An organizer can make this determination either at the time a meeting is scheduled or after the meeting is started.