I am trying to add an LHY Rpi Pro. with Volumio Premium. At first I used an I2S cable to my Denafrips Enyo dac. I have switched to a USB cable between them. Is it possible to remove these? LHY now directed me to set my Primare CD15. It shows up as a Chromecast.
No, I don’t think there’s any way to remove endpoints from Roon. You can disable them.
These are discovered devices on your hardware, as reported by the OS. Nothing more. If you do not enable them, they won’t be available as endpoints in Roon.
If they were enabled, but they are not. 
Roon is merely showing what Volumio reported as available endpoints on the RPi. Leaving them available but disabled won’t cause any problems. To actually remove them, you’d have to do it from the Volumio side with startup configuration files.
Are you able to play music directly on Volumio to the DAC over USB? It would show that Volumio actually recognizes the DAC. On Volumio, turn off I2S DAC in Playback Options, and reboot. When you connect the RPi to the DAC with USB, the DAC should be listed on Output Device in Volumio Playback Options. Select the DAC and play some music using Volumio. If this doesn’t work, it won’t work with Roon either. If it does play music from Volumio, go back to Roon Audio Settings and look for the DAC again.