Have you gotten Roon ARC set up properly so that it will play to your Android phone over cellular when away from home? That is the first step. After that, you might be able to get it to play in your car.
Roon has not introduced a CarPlay or Android Auto integration for Roon ARC as of yet. It does work to a degree with CarPlay, but I don’t know about Android Auto. If not, does your car have a 3.5mm aux input jack. If so, you can probably use that to connect to your car’s sound system.
Reviewing this it appears ARC is not configuring itself automatically to work outside the home. I’d suggest you open a post in support category (or maybe a mod can move this). Solving this will require “jargon” however. When ARC does not automatically configure itself there can be thousands of reasons and narrowing down the problem requires at least some jargon.
You can try looking through this known list of things which others have done to work with specific hardware and Internet service providers.
Bill_Janssen
(Wigwam wool socks now on asymmetrical isolation feet!)
11
I have this terrifying vision of thousands of audiophiles in overpowered luxury sports sedans careening all over the road while trying to navigate Roon’s UI on a tiny panel to the right of their steering wheel…
Or the left side, I suppose, in the British realms.
Are you sure you have ARC working correctly for remote access? Show us a screen shot of what you see in he Settings → Roon ARC window. That will tell us a lot…