12 days ago terzinator posted a link about Moving to a new server (core). I assume you’ve read it.
I’ll speculate that some of the difficulty you’re encountering are the changing terms for core, server and roon controller and roon.
AFIAK there is only 1 Roon App now that performs all of the above. You install Roon on the machine you decide to use as “Server” and also Roon on the machine you want to use as Controller. The “Server” will handle the DSP and convolutions but the settings are done from the Controller machine.