I think you're taking way too much stock in your "Fresno State masher". He's not going to see many carries. If he sees any it will be at the goalline--like Brandon Jacobs. However, don't you all still have Anthony Thomas to do that? If Marshawn Lynch struggles, he's going to be given the whole season to break out because he was a 1st round draft pick and a lot of money was invested in him. Rather than, at the first sign of struggle go to this 3rd rounder. It just doesn't work like that. I think Marshawn could possibly outrush Brown, but that depends if the philosophy is to pound the run.
With the advancement of Losman, and with a solid WR core lead by Evans, I'm not so sure running the football is priority #1. Here in Miami, Ronnie Brown is going to be asked to run the ball 25+ times again. Something he's never seen here in Miami. He's averaged about 1000 yards his first 2 seasons on very few carries. The Buffalo line is better, but I think Miami RBs will beat out Buffalo RBs, in terms of yards, just based on carries alone.