You should be able to go into the TVs settings and turn off bluetooth. Generally speaking, when a device capable of bluetooth audio is on and set to use bluetooth, it will automatically connect to the last bluetooth device it was connected to that is in range.   Alternatively, you could turn Roam off when you don’t want to use it.

Personally, I think Roam is basically working how I would expect it to.  I don’t use a ton of bluetooth devices, but they all seem to work this way.  When the source is on, and the sink device (speakers, headphone, watch) are on, then the two automatically connect.  I get that your use case is different and not how people generally use bluetooth speaker.  Perhaps some sort of compromise would be that you can set the Roam to automatically disconnect from bluetooth when charging.

Tahnk you, melvimble,

Yes, my case might be special but if roam does what I want to do then this is great for me. But, I think selecting wifi or blutooth (not wifi and blutooth) is a better-to-have feature, and if this selection could be done via Alexa (or Sonos voice assitant) then it would be much better, ....

In the hope that somebody will give me the other clue,

- I connected TV and blutooth transmitter via SPDIF, and the transmitter power comess from TV (USB). This is because when I connect roam and TV directly via blutooth, the sound will not come out from TV. What I want to do is that the TV sound comes from TV and the roam in kitchen.

- I do not want to turn off roam, just because it cannot work as a Alexa device when it is turned off.

Anyway, I will power the transmitter from an independent USB charger, not from TV, and control the charger by using a smart power swicth.