We use data from 220 individuals in 45 teams to examine team member roles as a cross-level linking mechanism between personality traits and team-level outcomes. At the individual level, peer ratings of task role behavior relate positively with Conscientiousness and negatively with Neuroticism and Extraversion. Peer ratings of social role behavior relate positively with Agreeableness and negatively with Openness to Experience. At the team level, a composition process of aggregation operates such that the mean for social roles corresponds with social cohesion. Compilation processes of aggregation also occur, as the variance of social roles corresponds negatively with task performance, and the variance of task roles corresponds negatively with cohesion. Skew of the distribution for social roles within each team—a measure of critical mass of members individually enacting the role—also correlates with social cohesion.