If you are running a second Roon Core, this was discussed here previously:
You just use it and it’ll ask you to unauthorize your old Roon Core. You can flip flop as many times as you want, but you can’t use both at the same time.
However, since you are running on a Chromebook, my guess is that you are running the Android build of Roon using ChromeOS’s Android support. Roon for Android does not support Roon Core functionality. It is a remote only.
There may be another way, using ChromeOS’s “Linux mode”. In this situation, your ChromeOS device is no different than any other Linux machine, and you could theoretically run Roon Server there.
You’d still need a remote, but it sounds like you have that working via the Android app.
The big caveat here is that Linux mode is “beta”, and may have other issues related to networking and discovery. Also, what Chromebook are you running? My guess is that it’s very much underpowered for running a Roon Core (unless it’s one of those awesome Google PixelBooks).