Abstract: A fully rotary engine adaptable to internal combustion or operation from an external heat source is provided wherein a drum-like housing containing a plurality of roller vanes contacts the inner surface thereof with the contact being maintained by a cylindrical inner race. At each end of the housing a torque plate, having a centerline offset from that of the housing and vane guide grooves which control the distance between each pair of roller vanes, transmits the rotation of the roller vanes to an output shaft running through the center of the torque plates. Rotation of the output shaft is provided by alternately increasing and decreasing the distance between adjacent roller vanes through expansion and contraction of a contained gas or through combustion and exhausting of a fluid/air mixture.