It goes without saying that the Scoring System of the League you play in dictates the value of Rosenfels, as does the Team you build around him, the type of player you are, and where you find yourself/your Team, in Week 11...
He's a solid definition of a high-risk, high-reward play at QB, so if you're League doesn't penalize heavily for INT's, and your starting lineup can absorb the risk if you guess wrong, and it's not the most critical game of the year for you, he's worth consideration.
Here's my situation: I drafted the Matt Ryan and the Schaub/Rosenfels Tandem as backups to Romo in a High-Stakes Local League where TDP=6, and there are no penalties for INT's. QB's are huge in this League. This is the 1st Week I've had to make a decision at the position, and I'm starting Rosenfels, no question. Now, it helps a great deal that I'm 9-1 and have locked up my Division, but I'm still competing with a few other Teams for 2 Byes, which are crucial because the loser of the Week 15 Games gets their money back ($500), and I'm in contention for Season High Points, which is another $500. So this is by all means a crucial week and a crucial decision.
Here's my analysis: I'm not keen on starting Romo on the road in his 1st Game back, vs a Team that's quite possibly the most heated rivalry in the NFL, and a lot of pressure on teh Cowboys. Ryan offers a very tasty matchup at home vs Denver, for sure. I'm going to bet they pound the ball with Turner/Norwood, and play a very efficient style of offense...but it's the combination of Sanders returning for Indy, and Slaton beginning to look like he's hitting the 'Rookie Wall' that has me intrigued by the Rosenfels vs Indy matchup. I'm willing to take the gamble that Rosenfels won't get hurt, and that it's extremely unlikely he'll get pulled (Kubiak knows what he has in Sage, and that the picks are part of his game), and the fact that not only does he have AJ and OD, but one of the best complementary WR in the game in Kevin Walter, and the emerging David Anderson. I'm thinking Sage might chuck the rock ~ 50 times on Sunday, with a minimum of 2 TD (and probably 3 picks, which don't matter to me), and over 300 yards. I'm going against Brees, but based on the rest of our Teams, I'm pretty confident that I'll get more out of Rosenfels than I will out of Ryan, and it will be enough to keep pace with my opponent.
My .02, hope it helps.