Yeah, that poor guy/gal looks dehydrated because of the root loss! Here's what I've read and heard to deal with this situation: You can drench the roots in a liquid rooting hormone like Dip n' Grow or something similar to help induce some new root growth. Let it sit with the liquid hormone for approx. 1 hr. You can then repot the orchid in fresh medium and put the potted orchid in an enclosed terrarium or empty aquarium with damp sphagnum or pebbles in the bottom to increase humidity to 100% OR I've also heard of people putting the orchid un-potted into a plastic bag that can be zipped closed with moist sphagnum and closing it up for a while to help the roots get started growing again in this 100% humidity environment. For disease concern, you can spray the leaves with a disinfectant solution prior to putting it in an environment with 100% humidity. It's going to take a while for the orchid to bounce back, so be patient. I believe the main thing is to try to keep it in a 100% humidity environment to help the leaves not dehydrate so there is reduced stress while more roots grow.
Hope that helps!