That’s correct.  The Sonos app is a controller, not a music player.  It only instructs your Sonos speakers on what audio to stream  directly.   It’s possible to connect both your phone and Roam speaker to WiFi in a hotel room, and then you would be able to access your Sonos playlist (stored on the Roam), but most hotel WiFi setups don’t allow peer to peer networking (your phone talking to your speaker).  To get around this, you would need to bring a travel router along with you.  So it gets a bit more complicated than just using bluetooth.

I also assumed the SONOS app would still “see” the Roam speaker and allow me to stream to it from my phone or PC music library. 

Consider the use case of streaming music stored on the device that the SONOS app is running on (phone or PC); playlist is comprised of tracks from the locally stored albums.  The SONOS app in this case IS the music player.   

There is no system reason why the SONOS App could not ‘stream’ to the Roam over bluetooth rather than wifi; in fact the whole reason for the Roam bluetooth connection SHOULD have been to negate the need for road warriors to set up travel-routers (which I used to do with a SONOS One.)

I appreciate the use case of streaming from third party service providers (Spotify for example), the SONOS App functions as a ‘controller’ and is not in the series path of the media stream.  But even in this use case, the SONOS App could proxy as the “speaker” and map the incoming  media stream over the bluetooth connection to the Roam. 

Hopefully the SONOS engineering team is working on supporting Roam in bluetooth mode from SONOS App.   

Otherwise, there really is no differentiation in Roam as a bluetooth speaker from BOSE, JBL, well … you the know infinite list of bluetooth speakers. 

So here I sit, in a hotel room, streaming to my Roam from my phone via bluetooth, using TuneIn.  

No, it is not.  The app is still just a controller, with the Sonos speaker accessing the music source directly.

Of course there are reasons.  The Sonos app is a controller, not a music player.  If you make it a music player, you now have licensing issues with all the streaming services who already have a music player app for you to use.  You likely can’t access your local library anyway, since you aren’t on the network.  if you can, there are plenty of other apps for that.  Only thing you couldn’t access would be Sonos radio.  Not sure why you would need a travel router, except for the convenience of using the Sonos app as a service aggregator.

Besides the licensing issues already mentioned, Sonos has to development and maintain what amounts to a free music player, since the app is free.  There could be no restriction on playing to the Roam, since you would have the option to play on any bluetooth speaker or use the phone speakers themselves.  And the next thing people will be asking for is to be able to use their phone/tablets as rooms in a Sonos home network...since it now does anything a Sonos speaker can do.

Pretty much true, except that it doubles as a home smart speaker and can share bluetooth audio with the rest of your Sonos speakers.  But you are correct.  If you have no interest in using anything but bluetooth with the Roam, it has little advantage over other speakers, except perhaps in sound quality...depending on who you’re comparing to.

Why is that a bad thing?

Why can’t I use the app to control the volume on the roam if the app is just a controller?