Q.Christmas cactus
Why are the roots next to the soil real dark brown and are falling off. The plant hasn’t looked good since the last bloom. What do I do if anything

It sounds like the plant may be overwatered. Make sure the soil is well draining.
If the stems are rotting at the base, you could propagate the stems.
These articles will help you.
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/christmas-cactus-soil.htm
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/limp-christmas-cactus.htm
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/christmas-cactus-pruning.htm
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/woody-christmas-cactus.htm