Roller is a small Cybertronian reconaissance drone and one of three major components that make up Autobot leader, Optimus Prime. Optimus can control Roller remotely up to a 1200 mile radius, and his consciousness can transfer to Roller so that he feels he is actually wherever the drone goes. Though it can operate independently, Roller likely wouldn't survive without Optimus overseeing it. Since Roller is basically part of him, Optimus shows great concern for the little droid whenever it is required in the field. Roller does not transform, but does carry a photon cannon for defence.