Oh ye of little faith! A true pilot does not let little things like lack of ailerons prevent him from doing rolls

If you've got a plane with enough dihedral, you can get a pretty barrel roll out of a plane using rudder and elevator only. When you go to try it for the first time, though, do it about seventeen mistakes high, and be prepared to cut the throttle and pull up, because you'll probably end up with the plane heading straight for the ground on the first few attempts.