Greetings!
Since my ROTEL RSP-1582 processor has zero network operational support for volume control, I couldn’t resist but to try your extension.
So as a public service announcement:
WARNING
This script will do unpredictable, potentially damaging things using a ROTEL RSP-1582 with this ROTEL Volume/Source Control extension.
In attempts to making this work, the extension would run, but I didn’t see any place in Audio to make control of amp. Further attempts, after starting node had the processor go batsh*t crazy with volume control, to a level I never had my system too. Was able to pause play in Roon, but…
EWE THAT SMELL…
The LR surround speaker (woofer) went poof, and opened… 
I wanted to upgrade anyway, and get a pair of Martin Logans for the rears…
So If you have an RSP-1582, please consider yourself warned.
That said, I still want to make this functionality work, but it seems the running extension/script will block all inputs from RSP-1582’s front panel or remote. It was bizarre.
For the life of me, I don’t understand why Rotel didn’t have a decent app to control this guy, without having to go Control4 or some other sublime thing…
My little Yamaha (7 Yr old) receiver has better remote CAT5/network control with their little app for Android/Apple.