Because of the contact area between the cam lobe and the lifter functions differently, there is no material where you need it to grind the roller profile.
On top of that the cam core chemistry or metalurg is different. That is why most roller retro fits need the distributor gear replaced. Some build a core with the roller metalurgy but put an iron distributor drive gear and end bearing on the core. This works for Chevys and rear distributor Mopars. BBM and Fords do not lend themselves well to this.
