I figured this would probably be the best place to ask.
The only place I've found online that even gets into is fangraphs. However, they very rarely ever actually gave formulas, it's mostly just words, which is very annoying. Would be so much easier and efficient if they just posted the formula then explained the variables.
But I digress.
At -> http://www.fangraphs.com/blogs/index.php/pitcher-win-values-explained-part-seven
He does give the basic formula for SP, which is (((18-AIP) * LRPG + AIP * FIP)/18)+2)*1.5
AIP=Average IP per start
LRPG=Leage's average Run Per Game
and FIP=Fielding Independent Pitching.
This is the part that should be different for RP. Afterall, you can't have an average IP per start for RP lol. But what's the formula for this part for RP? The rest should all be the same, outside of the league average win percent added for RP, but that's addressed in an earlier posted (.470%).