Power just in general....
The rocker takes say(just for example here), 1" of lift from the cam, and it turns it into 1.3" or 1.2" for the valve. It does that through pivot point location.
So that allows more flow into the combustion chamber, which = MOAR POWAH!
It acts like a higher lift cam, plus it also helps keep the cam from having crankcase clearance issues.
They should come in tomorow ..does any one know if the roller gain on the low end or top end power