You can wait until the plant finished blooming and then when you repot it, trim off all the dead roots..it's not necessary to trim off any roots now. Your plant will be fine.
I have a phal that has been in the same pot and medium for years and the medium was all mushy and decayed. I couldn't wait to repot, thinking the roots inside were probably all dead and rotten . When the last flower finally fade away, I feared the worst and did not want to look inside the medium. To my surprise, it did not have one bad root in the pot, the worst ones were the ones sitting on top of the medium , they did not look that great.
So I really don't think you have anything to worry about now with the roots and all..phals have vigorous root system and if you lost one or two..more will grow back. It's the growing season for phal now , and they are breaking out with new leaves and roots everywhere , quite a sight to see. Good luck
