So Roon can connect to a Wiim that's ethernet connected but at the same time, Roon can see that the Ethernet connected Wiim also can be streamed via Chromecast or Airplay.
Honestly, I don't get this part. The WiiM Ultra doesn't support AirPlay and it never did with any production firmware. Maybe I got that wrong? I'm not a Roon user
It's understood that as soon as you connect your Ultra via Ethernet it no longer works with Room while it does when using the Wi-Fi connection. With an Ethernet cable connected the Ultra's Wi-Fi is (and always has been) turned off. That's normal and it's unrelated.
If I connect an ethernet cable into my Wiim it will disconnect any wifi connection including Chromecast and Airplay.
I cannot make sense of this section. As per above, the Ultra does
not support AirPlay. Chromecast is supported but does not (and never did) require a direct Wi-Fi connection from your phone to your Ultra. It does require a Wi-Fi connection from your smartphone to your Wi-Fi access point (most likely integrated into your router) and
any network connection from your router to the Ultra, be it Wi-Fi or Ethernet.
The only precondition for Chromecast is that your smartphone and your Ultra must be on the same
logical network (which is not the same as all cables go to the same router) and all the protocols and ports required by Chromecast are
not blocked.
Are you saying that - independent of Room - Chromecast from your phone to your Ultra no longer works with the ethernet cable connected? If so, then this is the proof of a network related issue.