I think I see what you're trying to do - estimate the extra weight of the roller valve train and adjust spring tension to suit: 15% more weight needs 15% mote spring tension, etc.
It's far more difficult than that, the mass of the reciprocating segment of the spring (not all of it) is included, as is the reciprocating mass of both ends of the rocker arm. If that's not enough, you need Cam Doctor to analyze the lobe shapes of your roller vs. a lobe with a known spring recco for acceleration and velocity.
