Took delivery of my Sonos Roam today and discovered I can use it to sync Sonos with Amazon Echo Multi-Room Speaker groups. This is what I did:
Connected an Echo Flex to the Roam via Bluetooth (the Echo Flex is part of an Echo Multi-Room Group).
Played from Spotify to the Echo Multi-Room Group (including the Roam from the Echo Flex via Bluetooth).
Played on all my Sonos speakers by grouping with the Roam in the Sonos App.
Result: Synced musics on all Echo and Sonos speakers!