Brown would definitely fill the backup RB role. He would also be a guy who can spot start as needed, unlike Jerious Norwood. Brown has an history of injury in his career, but he played in every game last year.
He didn't play as well as he has in his career before though. He averaged under 4 yards per carry, and only totaled 734 yards as the starter. Prior to that season though his lowest yard per carry average was 4.2, and he has scored 23 TDs over the last three seasons.
This would be a good signing in my opinion. He would be a great backup RB because he has good speed and power. Usually with backup RB you get one or the other, not both.
He is 29, which is around the age RBs start breaking down, so some might not like that the Rams would have two declining RBs, with Steven Jackson at 28, but with adding Harvey Dahl as a mean and nasty guard, it should help those two backs greatly, if in fact we do sign Ronnie Brown.
One thing is certain though, we will sign a RB eventually.