It's not a worst idea, it's a non-idea. I did a slo-mo of him in NFLE. About the only thing he can do at an NFL level is hand the ball off to the RB. Routes, timing patterns, avoiding interceptions, and accurate throws are not in his repertoire.
Here's my take: He's a better 3rd/emergency QB than the guy we currently have (Bramlet?) But he'd never be second over Cassel. If we're keeping 2 QBs, then Rohan can forget it. But if BB does want three, he's a better choice than Bramlet, IMO.
I always respected Rohan for his dedicated effort but in the NFL he wasn't a very quarterback. He's big and has a gun but he lacked the combination of skills that sees other QBs lacking such outright physical qualities succeed.
Bramlet may have the right mix of skills to be even better than Davey in a total emergency circumstance. We know for a fact that Davey really can't contribute very much, so why do folks want him back? Think how bad Bramlet would have to be to be worse than the Rohan we know and didn't like.