I honestly think it's the Dillon dies. It says they start as a taper crimp and if you keep increasing the crimp, it makes a roll crimp. Not sure about that.
So far I haven't been really impressed with my 44 magnum Dillon dies. I have got the crimp die cranked down pretty good to keep my 44 bullets from crimp jumping due to recoil. Using Lee dies in 357 magnum, I have no problem.
I've got lots of Dillon dies and for semi-auto rounds I think they are great. For sizing and seating, I think they are pretty good ( though I do like the fine adjustments of other seating dies better). As for their crimp dies, I have no problems with their taper crimp dies. For roll crimping my 44's, I'm going to switch to either a Lee Crimp die or a RCBS roll crimp die.