Interactions in social roles typically involve the exchange of information. Those exchanges create coordination problems. A coordination problem is a situation in which each person wants to participate in a group action but only if others also participate. The relevant group action in social-role-mediated exchanges of information puts conditions on the flow and use of information. It is easy to solve such coordination problems when it is common knowledge that parties will all conform to the conditions. People’s presentation of themselves in social roles create such common knowledge that they will conform to standards of thought and behavior associated with those roles. We offer six examples of how common knowledge solves the coordination problems that typify social role interaction.