If i had to take a bet I would say most players are proably using them. I have several friends that have their own bat rollers for use with softball. Bat Rolling can have a positive effects on bats but also negative. bat rolling breaks the bat in evenly all over the bat instead of a player having to go take 500 cuts but it also makes a bat more likely to crack. It is almost impossible to detect unless you roll the bat to much and it makes the round bat shape like a stop sign. The real danger comes when you can take a composite bat and shave the inner walls down making more of a trampoline effect which can add anywhere from 25 to 50 feet on hits. Only way you can detect this is to weigh the bat (but a good bat dr. will put weight in the end cap, or measure the diamater of the walls. So you cant detect from sight. Heres a website for softball and you can see the changes the work can do www.worldshottestbats.com