I really don't think Rosalyn is the final Cylon. Here's why.
A few episodes back when she had her shared vision with Sharon and the Six, both she and Sharon were chasing after Hera only to see her get picked up by the six and Baltar and taken into the room where the final five are. We've seen the white sheets leading up to all of the glowing final 5 several times.
She can't be outside and inside that room at the same time.
Your right about that cause they did show the 5 but they were bathed in light. Now my possibilities of who the final one is changes... What if its Lee's brother he never died was in hiding and he knew he was a Cylon and he is waiting for the right time to return... I wonder when we will know who the 5th cylon is... how many episodes til the big reveal?(500th post)