Very true that roller cams have alot more lift per DUR than flat tappet cams.
Except those pesky stock roller cams
Even comparing aftermarket cams the increased lift per duration is minor.
Using the PO's advertised duration @ 0.050 number, 235, I compared two cams from the same manufacturer, Howards Cams Rattler for the B/RB.
0.050" more exhaust lift and 0.42" more intake lift are the only differences, well that and more than double the price for just the cam.
So I looked at the same cams but for the LA.
Exactly the same specs as the B/RB cams across the line.
What I think you means is the RATE of lift can be much quicker with a roller. It can open it faster and hold it longer than a flat tappet cam. But that isn't a spec cam makers really list.