If Rose and Bernard (and any other 815ers) are still alive (I hope), they should be in 1977 with Sawyer and Juliet. They would have experienced the same flashes in time, just like Jin did, so would have ended up at the same point in time when Locke turned the wheel.
We know they're not part of Dharma. Wait, do we? Maybe we just haven't seen them yet. Let's see... Rose is busy inventorying supplies and Bernard has found his inner artist and is Dharma's interior decorator. Seriously, it's possible they turned up and LeFleur said they were part of his ship's crew.
Or they are living in the wild ala Rousseau. This just doesn't seem likely to me, but it's possible and could point to them eventually being "Adam and Eve."
Or they have joined the Others. I favor this because I think this middle-aged couple would be better off with the Others than living in the jungle.
I just hope they turn up again.