That is correct so far but…
There is a Roon Extension from @Boris_Schaedler ( Roon Extension: Rotel Volume/Source Control - Tinkering / Roon API - Roon Labs Community) that allows setting the volume of the Rotel Amp by Roon. I think a scenario that should work for you would look like this:
- Get a Raspberry Pi that runs the rooExtend SD-Card image and activate rooDial there. With this device you can control Roon.
- Get a second Raspberry Pi running the Extension Manager from @Jan_Koudijs ( Let me introduce Roon Extension Manager 1.0
(currently v1.1.1) - Tinkering / Roon API - Roon Labs Community) and activate the Rotel Volume/Source Control here. With it you can control the volume of the Rotel from Roon.
With this you will be fine.
In release v3.0.0 of rooExtend (coming probably end of April) I will integrate the Extension Manager. After this there will be no more need for two Raspberry Pis any more.
Best DrCWO