I saw that Newcomer Racing has come out with roller camshafts for 4.0/4.2s. Not at all cheap, but sure beats having to build an engine with a flat tappet cam twice with the poor quality of new flat tappet lifters. Looks like they have the same offerings as their flat tappet cams. I don't know if I'd ever buy one, but it is still cool to see more modern offerings for these engines.
For anyone interested:
https://www.newcomerracing.com/store/p49/Billet_Roller_Cam_and_Lifter_Kits_4.0_4.2_Jeep_AMC.html#/