I am determining pushrod length on my 360, but the following info should apply to any engine with pushrods and overhead valves.
First setup had the rocker arm roller contacting the center of the valve stem. With valve closed, the contact pattern started on the intake side of the valve centerline. Then the contact swept across the centerline and stopped on the exhaust side of the centerline with valve full open. Contact pattern width was 0.13 inch, valve lift was 0.523 inch.
For second setup, the rocker arm roller contact started on the exhaust side of the valve centerline with valve closed, the contact then moved a little further toward the exhaust side at mid valve lift, then the contact moved back toward the centerline at valve full open. So the point of contact at valve closed and full open was the same.
Now the contact pattern width was 0.08 inch (a 38% decrease), and valve lift was 0.534 inch ( 0.011 inch increase, thats a 2.1% increase). The rocker arm roller now rotates very little compared to the first setup, so side loading on the valve stem should be decreased an equal amount too.
Reading I've done said it's most important to have the rocker arm as perpendicular to the valve as possible (second setup), and not to worry if the contact pattern is not perfectly centered on the valve stem; although being centered and perpendicular would be ideal. FYI