Comp Cams and others make self aligning roller rockers that do not need guide plates. The cylindrical roller tip on these have flanges (like a railroad wheel) on each end of the cylinder to keep them centered over the valve stem. They have them to fit both 3/8 and 7/16 studs, be they screwed in or pressed.

I don't think you really need to go to screw in studs unless building for high revs - which generally also means high lifts and spring pressures.