With stock rockers, the fulcrum height and valve tip height is set. You measure the gap with a pushrod measuring tool, then add whatever preload you want (for hydraulic tappets) to that number.
For rockers on a threaded stud, you set the cam lobe at 1/2 lift, then set the valve open to 1/2 lift, set the rocker fulcrum-to-roller tip center square with the valve stem. Then measure with the pushrod tool and (add preload for hydraulic tappets)
Notice: I NEVER mentioned ''making the roller tip in the middle of the valve''. That has NOTHING to do with proper rocker geometry. NOTHING.
If the contact patch is too far off, you need new rockers, not wrong pushrods.