A rolling road is ideal if you want to set up the car to its optimal performance. Most garages including main dealers don't use rolling roads. All the cars i have worked on have been pretty much standard, so my methods have worked. I agree that when modding a car, it is best to use a rolling road, as that is the best way to get optimal performance out of an engine.
Whats the most i could get out of my vr6 without any head work or cams?