The emerging technology of group support systems has the potential to enhance the effectiveness of team work in organizations. One critical factor that has received little attention in technology-supported environments is that of the roles participants fill in meetings. This paper develops a theoretical model of roles in computer-supported meetings and examines the impact of a group support system on roles. An exploratory field study of 10 work teams was conducted to investigate the perceptions of participants about their own roles and the roles that the group support system technology might fill. The study found a gap between the role expectations of meeting initiators and meeting participants, as well as between participants' role expectations and actual roles filled. The group support system technology was perceived to fill an unexpectedly large variety of roles. The study also showed that the group support system assumed some of the roles that participants expected to fill, resulting in fewer roles filled by participants.