^^^This. Without a cannelure to "roll" the crimp into, you aren't really making a roll crimp. Attempting to do so probably will lessen the neck tension your have and make the bullet more prone to "jumping" crimp.My experience with this has been unless the bullet has a cannelure that you can crimp the case mouth into you pretty much have to rely on case neck tension to hold the bullet so a roll crimp doesn't really offer much advantage.
Jumpin' crimp in a revolver is something that generally happens with heavy bullets over a heavy powder charge. A moderate .45 ACP load is nuttin' close.