I have used that bit on a horse that is not only strong, but also very unrelaxed in his mouth/poll/neck. Without relaxation, I got very few seat signals through to him. I didn't find that it helped. I switched to a sweet iron eggbutt snaffle and it helped a lot more. I also used a flexible mullen mouth bit and that was also better than the roller mouth.
One thing I don't like about the bit you posted is it's straight so it has a greater chance of coming in contact with the palate when engaged and then laying on the tongue when the contact was looser.