If a plane with a propeller, e.g., a Spitfire, does a constant barrel roll in the same direction as the propeller, will the plane travel faster as impractical?
The plane will fly slower
If the plane is constantly rolling, then both ailerons are extended into the slipstream, causing drag.
During approximately 1/2 the roll, the plane is in knife-edge flight. In that condition, the aircraft's fuselage is providing lift. It's a very inefficient way to fly and usually involves a significant nose-high attitude (more drag).