mjw
(You want nice, supportive? Call a damn helpline.)
2
Welcome to the Roon community, @Gav_Reid.
I suspect you built each Mac using Time Machine. This would copy a unique ID onto each machine.
The solution is to completely remove Roon from those machines, and install using the official installer.
Please use these instructions, but first, create a backup of your Roon database using the Roon app.
It is recommended to exclude Roon from Time Machine backups.