First,
There is a big difference between "juicing a bat" and rolling a bat.
In the slow pitch world they will remove the end cap and "shave" the inner wall of the bat to give it more flexibility or "pop", which makes the ball jump off the bat. This will usually increase the distance of a ball by about 10% or more. In the slow pitch world that makes a miss a home run for the big hitters. It will also decrease the swing weight of the bat by 1/2 or 1 oz. They then glue the end cap back on, very, very hard to detect.
Rolling a bat just breaks the bat in quicker. It breaks the composite fibers, making the bat "livelier" if thats a word. This can be done without rolling it by taking "alot" of BP. Most composite bats do not get broke in until they have 300 to 400 swings on them. Once they are broke in, the bats life is short. They will break in half or cave in. This can also be done by beating the bat "not too hard" against a wood light pole or the like, turning the bat after every swing. Having a bat rolled, just speeds up the process and is impossible to detect because the result of rolling it is a natural result of composite bats.