You can see details of home assistant here: https://www.home-assistant.io/
It has a sophisticated way of setting up rules of the form ‘if this happens, do this’.
It integrates with multiple remote control switches and sensors, I use a mixture of zwave and zigbee.
They have a phone app which allows you to detect when home owners get home.
If you have a ROCK you can use a mixture of WoL and rest commands (both available in HA) to turn it on and off. Basics here Roon module for Home Assistant - #318 by GregD
I maintain a Roon integration that connects HA to Roon and allows you to see the status of roon endpoints and send ‘play’ commands. Details here RoonLabs music player - Home Assistant
So if you had a ROCK you could do presence detection via the app to know someone arrived home, use WoL to turn the ROCK on, wait for it to start, and then send a play command.
Otherwise I think my HA integration will disable roon endpoints in HA when it sees your roon core has shut down, and enable then when it re-starts. So you can use the enabling of an endpoint as a trigger to start playing.
Hope that makes sense.
There is a long thread about HA and roon. It starts as it was being developed, but later posts describe how people are using it: Roon module for Home Assistant