I've ridden rollers untold hours over the last 20+ winters and may be a little biased, but here goes;

How often have do you lose your balance on the rollers during one use? None

How many times have you been injured using the rollers? None

Would you be interested in a stabilization device that would help support the bike, but could be adjusted to allow some movement? No

How much would you be willing to spend on such a device? $0

Where would be the best location on the bike to clamp for stabilization? I wouldn't.

I think you are seeking a solution to a problem that doesn't exist.