do NOT crimp smaller than the diameter of the cannelure. If you crush the case mouth into the jacket you can end up worse than not crimping at all.
Non cannelured bullets shouldn't be roll crimped at all.
How I do it: I measure the cannelure measure the diameter of the bullet get the difference. That is the max value between an uncrimped case mouth and a crimped one. It doesn't take a lot of crimp.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent