When Japanese learners learn English communication, learning effect would change depending on whether their learning partner is Japanese or American, and whether he/she is a teacher or a peer. The role of the partner is important for English communication learning. To investigate how roles influence English communication learning, we have developed a system using a robot whose role can be designed. We have also designed its behavior according to its position and native language so that the roles assigned to it can become apparent. The results of a case study with the system suggest that the role of the robot being a peer or Japanese increases learners’ engagement in English communication.