@support I’m experiencing similar issues as others regarding the use or Roon with Sonos. I too am getting the “Transport: Roon lost control of audio device”.
My set up is using an iMac 5k i7 as the Core running version 1.4. I have a Sonos Bridge connected via a unmanaged ethernet switch. My Sonos transport device is a Sonos Connect which is connected to my audio system and connects to the Sonos Bridge via their mesh network. I use an Airport Extreme as my router and I have it set up to always assign the same IP to the Sonos devices when getting rebooted. I use an iPad, iPhone and a MacBook Pro for controlling the Roon.
The issue arises in a variety of scenarios. I often let Roon play in Radio Mode and it will for a couple of hours then for no reason, it will stop playing and give the the error message. Other times it will happen if I chose to skip to the next track. Note: This does not happen every time I chose to skip a track. Another scenario might be pausing the music when leaving my home, them selecting Play once I return I will get the error message. Again, this is not always the case. I’v had success multiple times when releasing the Pause command or using the Track Forward command.
I’ve noticed when this happens, I can go to the Sonos app and select music in Music Library then double click on the music and get it to play but without the Sonos transport controls being available.
I can always get things working again if I reboot the Sonos Connect.