Rotted roots are mushy and should be cut off to point where the root is solid. I do not cut all the root off unless they are mush all the way to the bulb. Roots will grow from the old roots. Be aware that dark roots do not necessarily mean rotted. They can be colored by the media they are planted in. Bark will turn roots brown as will sphag.

Roots which are dry can be rehydrated with a good soaking. I would not cut off dry roots.

Treat roots carefully and do not be too quick to cut them off. This is not a good time of the year to be doing major work on the roots. Plants in soggy sphagnum can be unpotted and left to dry out on newspaper and repotted in a clean mix without too much trauma to the roots.

Big box stores are notorious with their poor care. Best to find out when they get their shipments and buy them when they come in.

Jane

It is very troubling to hear that you are having trouble finding quality orchids. I recently purchased several bagged orchids from Lowe's (the Sun Bulb Company) ones and they have worked out great. I was lead to their product through research and can assure you that if your store is not up to par, which it sounds like it isn't then let the garden center manager know. Also, the weather conditions might have had a negative effect on the general up-keep of the garden center as well!

Try another store or check out where you can purchase the Sun Bulb Co. products elsewhere!
Good Growing.

It isn't the color of the roots that is important, it's the texture of the roots. Soft and mushy or dry and stringy, not good. Firm, plump and healthy, good. You were wise to only concentrate on the bad type of roots and leaving the rest alone. As Jane says, dark roots do not necessarily mean rotted. She gave you excellent advice.

I saw a batch of bagged cattleyas from Sun Bulb Co at Lowes back in November. The plants still looked fresh, so apparently the shipment had just arrived shortly before I visited Lowes. I bought a catt with nice healthy roots, and it hasn't done much all winter, though last week I just discovered a new bulging growth and a new root!

It is really sad how chain stores treat their orchids. The people at Lowes never bother to water the orchids at all! When I went to Lowes again in January, the same catts (from November) were there, sitting in a dark corner, looking almost dead from dehydration. There were also two dozen paphs, their media bone dry. Poor things.

Chain stores also carry highly stressed orchids that were forced to flower quickly, and after the pretty show, they quickly deteriorate.

Now I'm wary of buying at chain stores, but I'd buy Sun Bulb plants again.

About the roots...Sometimes it's hard to tell if roots are alive or dead just by looking. You can do another test: give them a gentle squeeze. If they feel firm, then they're good. Try to keep up the humidity around stressed plants (humidity trays work well). Good luck!