I snagged a set of roller rockers off eBay last year (came with anice cast valve cover and an aluminum bridge for the rocker shaft), and I'm using them now in my PV's engine. (2.2 liter bottom end, stock B20F head, Weber DCOE 40's, header, 2.25 in exhaust)

I took the car for a spin, installed the roller rockers (only about 15 minutes of work) and took it for a spin again immediately while the previous drive was still in mind. According to my butt dynamometer it didn't change the shape of the curve, just amplified it slightly - say 5% or so. Just a bit more torque all over the rpm range. It doesn't really rev higher now than it did before, the torque still seems to trail off at around 6500 rpm. Perhaps that is the stock valve springs starting to float? In any case, I usually shift at 6000 rpm.

I plan on getting a modified head (bigger valves, double valve springs, higher compression, perhaps reworked to match the 92mm pistons) over the winter and putting it and the R cam back in at the same time. I haven't spent a huge amount of time fine tuning the Webers at this point (they run evenly rich at about 12.5:1 A/F ratio) because I figure the new head and cam will change that anyway.