Snuffy,
I would NOT suggest using an actual roll crimp (into a bullet cannelure) on a .45 ACP that is intended to be shot in an auto-loader.
To the extend that the case actually headspaces on the case mouth in the auto-loader, the crimp MIGHT get pushed into the chamber throat/leade and not release the bullet at the usual pressure, raising peak pressure substantially when the round is fired.
Many people may follow this post with statements that THEY use roll crimps on the .45 ACP in auto-loaders all the time and never had any problem. And, for several reasons, that CAN be true. Often, the cartridge is loaded to actually headspace with a semi-wadcutter bullet against the lands, or the extractor will hold the case rim well enough to keep the case mouth from contacting the front of the chamber when the firing pin falls. In situations like that, a roll crimp is held away from the constriction of the chamber throat, and there is no effect on pressure. BUT, change how long the cases are (for instance, buy new brass) and then the saving factor may no longer be pressent.
So, on any essentially straight-walled cartridge that is to be used in an auto-loader, it is best to use a taper crimp that leaves the case mouth at the proper diameter for headspacing. If using a roll crimp die, then the idea should be to get the flare out of the case mouth and leave it at the same diameter that you would obtain with the proper taper crimp.
SL1