Michelle, I have never seen one "crispy and dead" make a comeback. If you see a green center, then there is a chance. The exception is with the heuffelii. Since multiple rosettes share a common root, the root mass can be much larger than that associated with a Sempervivum rosette. I've had one recent case (heuffelii), where all the rosettes bloomed and died, leaving no visible rosettes, where the root the next spring produced a rosette. That plant is still with me, but the rosette has yet to increase in the number of plants. I figure that I will see that next year.
I don't mean to be discouraging. Any green you may see is good, brown and crispy is bad and likley will not recover..
