Moving to the Mac Mini M1, is covered in the migration guide that was linked about and it seems you’re good with that.
Changing DACs, is not related to moving your core, you can regard this as a completely separate activity.
Thus you are fine to use the running Roon system that was loaded from the Roon Backup take from your old core.
They are both USB DACs:
When the Teac is disconnected it will no longer show in Roon as a audio device.
When the Rotel is connected it will show [as a new] device; the Teac should inform Roon via USB what’s it capabilities are, but it’s always worth sanity checking them in Roon.
So for 1 hour no sound. The Rotel was not recognised by the mini. I tried a different a USB cable. But still nothing. Then I realised on the Rotel, they put a USB and a PC-USB! So I switched, turned on everything and couldn’t believe what I was hearing. So great SQ.
THANK YOU Carl! I managed to do the restore of all my music. Everything is here and my new speakers are amazing: KEF R5! Wow good stuff.
I’m just missing some covers. But all good. Appreciate your help and taking the time to answer.