The options are to have something simple push the cam in from the front, or replace the freeze plugs at the back of the cam with some sort of contraption to pull the cam in. The "pull the cam from the back" option just seems a bit Rube Goldberg no matter how you set it up. Roller bearings may be overkill, but the whole adding a plate on the back of the cam to push against the block seems like more trouble than it's worth to begin with.