This paper presents a controlled experiment conducted with software engineering students that demonstrates the utility of forming teams based on R. Meredith Belbin's set of team roles. The overall research effort is a demonstration of the general utility of Belbin's roles in improving the effectiveness of teams, even industry teams. The significance of this work is twofold: performance and team viability. Performance improvements clearly improve a team's productivity; viability issues are important because if employees remain with a team or employer, then employee replacement costs are reduced. To address this problem, as an initial step, controlled experiments have been conducted to demonstrate that teams that contain certain roles perform better than teams that do not. In a laboratory setting, a number of teams were formed that contained a single leader; other teams were formed that had no leader or multiple leaders. The results of this single experiment are positive. They demonstrate that indeed Belbin's roles are useful knowledge in forming teams. The specific conclusion of this first controlled experiment is that a single leader on a team perform better than having multiple leaders or no leader. In other words, as one would expect, the mean time to completion for the leaderless group of teams was significantly larger than the group of teams with leaders. This means that Belbin's roles can be utilized in team formation, making sure that a team has a single leader, and also for evaluation on extant teams. Both of these aspects, formation and evaluation, are extremely useful to managers of software programmers.