You can stream from your phone using bluetooth, assuming your active speakers have a bluetooth input (You can pick up a bluetooth transmitter/receiver on Amazon if required).
Obviously you’ll need a generous data allowance as well.
In summary, Arc would be the equivalent of a Walkman for Roon at this point. However, decentralized lossless streaming, same with CarPlay/android auto, to name a few are actually the main issues-pain points affecting potential and current Roon users/subscribers.
You can indeed stream to AirPlay devices from ARC, at least from an iPhone running iOS 16. Once play is established via the phone speaker go to the lock screen and you should see the now playing notification box which should include the Airplay icon on the right hand side. Clicking on that should bring up a list of the devices which your iPhone finds on the local wifi network.
Roon endpoints not yet but I can see that being an evolution at some point to be able to cast to one using some system. You can currently use system AirPlay or Chromecast from a phone or tablet and stream to streamer or speakers that support it.
“Also, I have a second home and I would like to not have to take with me and install my Roon core in that network every time I want to listen to music there.”
I have the same situation. So I keep a Mac mini in each place running Roon, and carry a big (capacity) USB/Thunderbolt SSD from home to away, updating the music in away as needed. Then Roon lets you transfer the license form home For to away Core. For short stays, don’t bother updating the music…