Cherry roller bit?

[lisa_lou]

My 7 yr old mare keeps setting the bit in her mouth when schooling and coming above the bit often. I was wondering if a cherry roller might help me as she wont be able to get hold of the bit as im trying to achieve a constant outline when she is working.
I have heard that although these are a snaffle they can be quite severe, is this so?
Ive tried a D ring thinner roller that has copper rollers but its not dressage legal and would like her to be in a bit that is.

 

[Cobby Fan]

Hi a friend has used a cherry roller with her horse which was strong and would set its mouth and it has improved. i'm not too sure if they are legal for dressage though?