Looked like a standard revolver. One side of the cylinder would swing open (up). You would load the roll on a peg, then feed the lose end around and up to where the hammer on the gun is. When you pull the trigger, the hammer would pull back and a little lever would pinch the paper against a wall and then push it up as you continue to squeeze until the hammer fell against the powder pocket.

Unfortunately, for the ones I used anyway, that pinch lever wouldn't always advance the paper the right amount and I'd start getting duds every shot because the hammer was falling between the pockets. And then we would resort to the hammer.