A barrel roll is done with elevator, aileron and rudder. it's normally coordinated and symmetric flight, 1 g maneouver. view from the side, it looks like a roll, but not on a straight line, with a quite big 'hump' in the middle, view from the front, or back, it looks like a loop.

The plane climb and start like a normal coordinated turn, at the top of the manoeuver, the plane should be inverted and flying on a 90 degres course in regards to the course it had entering the maneuver. I like doing it with small inputs and large, I think it's very smooth and nice, not stressing the airframe at all. Contrarly to what some said, the plane should finsih the manoeuver straight and level, on the same course and altitude it started.

I think the most famous barrel rolll ever done was made by tex johnson ( if I remember the name well) during one of the demo flight of the Boieng 707 over Seattle.

Bernard