Mikrotik is Innocent OK.
Managed to get my Sonos Roam 2 setup by following these steps:
- Sonos App - force stop
- Sonos App - uninstall
- Android - restart
- Android - connect to network (on Mikrotik)
- Android - install Sonos App
- Roam 2 - Factory reset
- Sonos App - setup
Seriously weird behaviour!