Roll stability can be caused by having more side surface area above the vertical C.G.. Judging from the pictures of your craft, the vertical C.G. is just above the chines by maybe an inch. Most of the area of your rudder and v. stab. are above the vertical C.G.. So, when your craft rolls a bit and side-slips in that direction the greater surface area above the C.G offers more resistance to the side-slipping than the area below the C.G. thus righting the craft automatically. If you want more roll stability, add more area above the vert. C.G., but keep that added vertical area aft of the longitudinal C.G so you don't sacrifice yaw stability in the process. The chines themselves are probably adding to the roll stability too because they are angled out like wings with extreme dihedral.

From the video it looks like your craft flies a lot like a "pizza box flyer". PBFs are not too different than flying lawn mowers. My PBF was very stable at high angles of attacks (45+ degrees) too and roll-stable at all AoAs. Although it had elevons, I found that I could steer it around quite well with rudder and elevator input only because of this roll stability. In other words, aileron input wasn't necessary to fly it around. Aileron input was only necessary for performing certain aerobatics.

I don't have any video of my PBF, but here are a couple of pictures.