I would pull out that plant, examine further roots below, if there are additional dead ones, cut it off, then repot in a chunkier media and much smaller container preferably with side holes.
I have learned now to raise the plant's lower end higher and allow it to lean a bit, unless, it has no viable roots, then it needs to form those new roots to get access to moisture, so some would try to increase the humidity to encourage root formation.
So far from your photo, I see some good roots left. I will post here how my current Phals look in their containers. You will see how I have raised the lower end, and made the root zone really airy, short of mounting them..but I don't want to mount them, still in their container but at the same time keeping the root zone with good air circulation. Typically Phals that have just recently bloomed, will go on a rest mode, so be very patient, just water the media as needed; allow it to dry. Phal roots like that. I do not mist the leaves of my orchids, especially if indoors. Different approach to the other types I have during warmer weather and staying outdoors, those I can water freely whole plant. But indoors, I just don't do it. Invites more leaf problems.
I have been experimenting with media so, some containers will have bark mix, some have hygrolon baggies that I stuffed with styro peanuts and some clay rocks, some with chunks of lava rock..anything that can keep the root zone well aerated and not soggy. In your case start with bark mix, chunky ones, and adjust later on as you get the hang of it.
I just watered them thoroughly awhile ago, just the root zone, so most of the roots are in deep green color. Have run the ceiling fan too afterwards, to allow air circulation..my window is open too right now..weather here is nice at 74F
Different orchid growers, different approaches depending on our micro climates and locations..but one thing for sure..those epiphyte roots needs very good air circulation next to proper timing of watering and eventually proper application of fertilizer once it has recovered from whatever stress it is undergoing right now.
