The Triplane can be rolled but this maneuver gets difficult due to the differences in the control sensitivities of elevator, aileron and rudder. Lots of rudder correction is needed to overcome the adverse yaw. Once the roll starts indiscriminate use of the rudder or elevator will quickly stop the roll with some interesting results. The best rolls seem to happen when you use very little corrections once a roll starts. Big barrel rolls also seem to be better than rolling on a point.
Slow rolls are very difficult because of the control sensitivity.
The bottom line is, keep it fast and quick with lots of altitude for corrections if you fall out of one. This is another easy maneuver. With its quick response, the Triplane comes quickly around. Sometimes I can build up airspeed to 110 mph, haul the nose up 300, half roll at 80 mph and exit in the opposite direction at entry altitude. Inverted Flight, Negative G's, Tall Slides, Snaps, Etc.