Alexa should not affect Grouping of speakers. How are you starting the Grouping when Alexa is added? Also are you using an Alexa external device to control your Roam?
No external devices. Trying to group via app.
Goes wrong when I add Alexa. Works fine after I remove Alexa.
That’s extremely odd. Have you submitted a system diagnostic within 10 minutes of experiencing/ recreating this problem, and call Sonos Support to discuss it? But don’t post the resulting diagnostic number here, Sonos is sensitive about GDPR.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.