Always crimp revolver loads
I guess it all depends on what you mean by "crimp". For my .45 ACP loads, I taper crimp them so they measure .472 across the case mouth. They function like they should in my Bullseye guns and I can shoot them in my S&W Model 25-2 without half moon or full moon clips since they headspace on the case mouth.
The same goes for my .38 Special loads since I'm using a 148 grain HBWC for both my K-38 and Clark 1911 conversion. They feed just fine with the taper crimp; no roll on either the 38s or 45s.
Now, for the loads in my Model 629 with jacketed bullets, I do use a roll crimp to ensure that the bullets don't back out from the recoil.