Maybe not. Without diving into too much detail…
ALSA is the sound framework inside of Linux. Roon Bridge looks for hardware devices that ALSA has found. If the hardware device is compatible with Roon then it shows in Settings → Audio.
USB audio devices (Class 1) negotiate their capabilities (channels, resolution, bit depth, name, id, etc.) and ALSA is responsible for this negotiation. Only after this completes is the audio device assigned a hardware ID by Alsa and then Roon Bridge finds this and that’s your USB DAC in Roon.
The opposite is also true. When you power off your DAC Alsa detects this and removes the hardware device. Roon Bridge notices it leaves the lists and removes it from Settings.
Now, the problem is, you’ve got a lot of moving parts that have to occur in a specific order but are not always stable. If you power down the DAC then power it back up… Linux needs to see the new USB attach, Alsa has to negotiate capabilities and add the hardware device, and Roon Bridge needs to see the device and realize its the same one you’ve already activated (or it could land in settings waiting for you to activate it).
Some DACs work just fine to power down / power up all day long with Alsa. Others maybe not. To troubleshoot you’d be troubleshooting Alsa (aplay -L). You may have better luck with another distribution but since they all rely on the same things probably not. However, I think I made this statement before and someone proved by wrong when they loaded Ropieee and it worked perfect after having issues with another distro. Worth a try. Most of my DACs I leave powered on. The one DAC I do power off / on the Pi (dietpi) stays on and the DAC comes back just fine. So, this may be specific to the RME and dietpi.