You can certainly group two rooms at will in the Sonos software. Or, for that matter, ungroup them.
Note that any room grouped with a TV room, and playing an input from the TV, will be slightly delayed, by at least 75 ms. This shouldn’t be a problem when you can’t hear both rooms at the same time, in fact I’ve done this before with my TV room and my kitchen. As long as I didn’t stand in the doorway between the two, it was fine. And since I don’t have the need to stand in the doorway…
However, that same grouping, when streaming music from the internet (not the TV input), will be in sync, 100%.
Yes.
You would add the third speaker as a new Sonos Room and you could use it alone or you could Group it to play what the Beam and SL pair are playing.
Thanks for the replies. Roam is working great.