I think your over estimating the difference in 380 and 9mm when fired from sub 3" barrels.
If you do some research you will find that 9mm shot from a 2.7" barrel is barely faster than Buffalo Bore 380.
Of course it's a whole different story with longer barreled guns.
Matter of fact comparing Buffalo Bore 380 to Federal 9mm 105gr Guard Dog which is what Jeff Quinn recommends for Rohrbaugh R9, the Buffalo Bore 380 is actually faster out of a P3AT than the Federal 9mm is out of the Rohrgough.
Maybe not that much faster, but with a significantly heavier bullet, which is a pretty big bonus.
And Federal's Personal Defense line as a whole seems to be based around lighter than normal bullets loaded to velocities that would be considered light for a heavier bullet in the same caliber. Maybe a great choice for a Rorbaugh, but there are plenty of 3" 9mm pistols that can easily handle a regular load.