IMO it will be limited. The rolls and slap outs have little correlation, but you do learn to tuck your chin naturally. The concussions in football most often seem to occur when the back of the head hits the ground. Tucking you chin on impact minimizes that. If that becomes second nature for him that would be a benefit. Personally, I started in judo as a kid. I did that for a few years but then transitioned to other martial arts. Mostly striking arts, but ju-jitsu and MMA also incorporated falls and throws. I also played HS football and was involved in coaching (just one season) and scouting on the collegiate level. I don't believe most football injuries would be prevented by learning how to fall outside of learning to protect your head by tucking your chin. But learning that one technique would certainly have a benefit.