I was trying to use the Roon ARC in my car via CarPlay. Since I drive about 6,000 km per month, a traffic announcement (TA) that starts automatically is important to me. But it doesn’t work when listening to Roon ARC, although the TA turns on, it immediately switches back and I have to manually switch to listening to the radio twice in order to listen to the TA. When listening to music via Apple Music, everything works as it should. It seems to me that Roon ARC is dragging with CarPlay who will be in charge 
For this reason I am not using ARC for now.
Thank you for your reply and for moving my post to the correct category. I have been using Roon for a long time but this was my first post. I haven’t had a reason to post questions yet because Roon works perfectly. I use Waze for navigation and still use it even when I know the way, for the same reasons as you. Traffic Announcement (TA) is part of the radio and has nothing to do with navigation.