Can't really tell from the photo, but it doesn't look like root rot to me. The plant looks dehydrated which could be lack of watering. Some old roots, but nothing terrible. Even the bark doesn't look bad.

I would put it back in the pot, give it a good watering, a little fertilizer and put it in a bright window.

Jane

This Phalaenopsis you will put in a warm place, min. 20ðC/night, 25ð/day, humidity 70%. You may put it in bark or styro pieces. Or you do not pot it, spraying the roots with rain-water. Observe the development of roots, one root is already growing. If you water too much roots will rot, when right you will have growing roots.
Sensitive for light, shadow or max. half-shadow is ok. No fertilizer when the plant is not growing and does not have sufficient roots, fertilizer are for healthy plants ok. But this species is not demanding in terms of fertilizer. Half dosage is enough. Weakly weekly as some are saying. But, as mentioned, only if the plant is healthy. When more roots, plant could be potted.

An easy way to bring up the humidity to that phal. while it is recovering is to put it pot and all under some type of clear plastic cover. Many times the orchid is small enough to fit under a clear plastic dome from some baked goods that you bought at the grocery store. If not, you can put it in a clear storage box. I also put alot of damp (not sopping wet) sphagnum moss under that container as well. The container will get foggy with mist especially at night. This will keep it hydrated while the roots start growing and plumping up. I put a gage in there to watch the temperature as it gets hot VERY fast if the sun hits directly on the container.

These are all great ideas. I agree with Jane, it looks desiccated. You could trim off the extremely desiccated roots leaving plenty to secure the plant in the pot. Make sure you do not use a pot that is not any bigger than a 4" diameter.

Thank you for your ideas. I put it back in the pot and watered. I think I will try the "dome" idea for humidity, although I have it sitting in a humidity tray. It is in a due north window--very bright but no direct sun. Please let me know if you have any additional ideas.