roller rockers in general cut down on valve train friction....engine works more efficently...thus in turn giving slightly more revvs....
BUT, on higher ratio rockers 1.7, 1.8, 1.9. this increases valve lift, thus making the stock cam slightly bigger to allow more air in and out. that makes for a nice power increase.
scotty.....for shaft style rockers.... are they self aligning or non-self aligning? were they on another 3800 vehicle? just curious. if they ae NOT self aligning....you will require more parts.