what you probably heard was that margin of victory affects rankings. but it absolutely does not affect rpi. the formula for rpi is,
25% - your winning percentage,weighted (1.4 for road wins/home losses, .6 for road losses/home wins)
50% - your opponent's winning percentage (unweighted)
25% - your opponent's opponent's winning percentage (unweighted)
also, you don't count your game with your opponent when you are considering their winning percentage, i think. i can't remember exactly, but i also think you do not count your opponents game with your opponent's opponents when you calculate the opponents opponents winning percentage.