This study characterizes role assignments in maximizing a group’s winning probability under the influence of the complementarity of group members’ efforts in a group contest, in contrast to prize and multiple resource allocations. We use a constant elasticity of substitution effort aggregator function to parameterize the complementarity. While the prize and resource allocation rules depend on the complementarity, the assignment rule does not when multiple roles are assignable to a single group member: All roles are assigned only to the most productive group member.