I you use a higher ratio rocker, it increases the camshaft lift. BUT if you are replacing the cam anyway, why not get the lift you want? USUALLY higher ratio rocker arms is done with a stock cam and is considered a cheaper(though less effective) solution.
You also have to be concerned with the valve to piston clearance.
2012 Express CC Black 4WD 3.92 Posi, Bedrug, Backflip G2, Cut rear springs, V6 fan mod, 180 thermo, Diablo Sport