Mutant is giving you some decent advice
You do have enough roots for the plant to live. I have had one pull thru with only 1 root. I don't know if you have some garden sulfur powder or a fungicide, but after cleaning off the mushy rotten or hollow dead ones, I would wash the roots well, and try to apply a bit of sulfur to the cut ends or a fungicide. Some look like they have a bit of black and then a green growing tip, so I would want to prevent any rot that is thinking of starting. Failing that, a rinse with regular brown listerine might help. It is an antibacterial too. If you have some K-L-N rooting liquid or SuperThrive I would then soak the roots for a short while in water with this added. If you don't have it, I wouldn't worry if this is your only orchid, no point running out for some right now.
Then pot it in a pot only big enough to contain the roots. Over-potting and staying wet too long is the cause of root rot. A clear pot would be best as Phal. roots seem to like light. Since it is used to moss, I would suggest a mix of medium bark and some moss but other people use things like CHC or just bark etc. and it is what works for you in the end. If you use bark, it needs to soak overnight or for at least a few hours. If using only bark, remember it will dry out much quicker than moss, especially while it is new.
I think that will give you a start. also do not get water in the crown where the leaves join. I am wondering if the yellowing there is a start of crown rot, which would mean the end of the plant. Hopefully not and it maybe just needed to get out of that wet moss. Good luck and don't be afraid to ask newbie questions.