According to the SONOS FAQ, this only works in WLAN.
Additional to this:
If you connect the Roam via Bluetooth, the stereo pair will be disconnected. When the Roam is connected to the WLAN again, you have to create the stereo pair again.
Source: https://support.sonos.com/s...
It's better to keep your hands off the Roam. For its price, there are more reliable products. Roam's Wi-Fi and Bluetooth connections break down again and again, and the batteries have a rather short runtime.
My Roam was delivered yesterday. My mistake, that I didn't pay attention to the description of the Roam at Sonos, that the little thing only works with S2! All speakers sold after May 2020 should need this (according to Sonos support). My Move (bought before) was the last one I could connect to my S1. The new Homecinema I bought last year (Arc, Sub, 2x One) I also had to install with the S2. Now I have installed the Roam with it but of course I can't use it in the S1 group. But Sonos is at least too good to hold that you can install and use S1 and S2 (and thus the old devices as long as they work - with me already over 10 years!) at the same time. In my case, radio/streaming/music with the S1 and home cinema with the S2. I got the Roam anyway for mobile use with BT and Handi (but it has to be integrated into a WLAN for installation first - just S2; information from Sonos support).
Yes, as long as you control your existing ONE speakers with the Sonos S2 app. That's where you form a group with the two ONEs and the Roam/Move. The Roam only works with the S2 and the latest software (update). The Roam has a longer battery life (but I couldn't test it myself yet, as it was delivered yesterday) and is lighter, especially for mobile use. In my opinion, the Move has an even better sound. Especially outdoors on balconies and terraces, although the sound of the Roam is also amazing for this small thing ;-)