[Tom Line]

I know you've given up on the rollers, but let me give you a hint anyway as to what some teams figured out.

It's a whole lot easier to "wedge" the ball into 2 rollers so that it's actually held rather than trying to roll it backwards. Rolling it backwards depends on a lot of variables, especially the relative friction between your rollers, the ball, and the carpet. As long as the ball isn't off the ground when it's "wedged", you're fine.

Take a look at robowranglers video to understand better what I mean. Notice when they mistakenly drive up the ramp the ball comes off the floor? They're not spinning the ball - they've got it wedged.