I don't understand this signing one bit.
For the Raider's it's a waste of money. At best Rhodes is going to be a 50/50 guy with Lamont. And they have a lot more serious problems to address than just the RB position. Hell, one could argue that RB is the only position on the entire TEAM that didn't need a major overhaul.
For Dominic, I think this contract signals the end of his career. Maybe he saw the dollar signs and decided to go for it, but if you factor in his potential for another payday two or three years down the road, Rhodes is probably coming out behind in the long run. He could have signed in NYG for less for instance, stuck around a couple years looking pretty good on a pretty good team and then signed on as a backup somewhere else for another few million and another few years worth of NFL.
I mean seriously, Oak not only has Lamont, who just took a paycut to stick around, but they have one of the worst O-lines in the league, no QB, and no bright prospects for the future. Surely Rhodes could have gotten similar $$ elsewhere in a much better situation.