The non-Roon music apps I use on my Android phone (Spotify, GoneMad) have widgets that you can use to control playback, including hitting play to resume the playlist or album you were playing during your last session, sometimes a pause button, and controls to skip to the last/previous track.
It would be great to see something similar for ARC!
I had a very quick play with KWGT widget builder. Can get a widget working to open Arc and show “now playing” album art but could not get the toggle play / pause etc to function.
Had similar issue in Tasker for creating a command for car bluetooth connection to auto start playing Arc in earlier builds. Toggle play would not work, however, it started working a few builds back and still does.
Edit to add: play / pause / back / forward for Arc does work in KWGT widget builder.
Not sure how familiar you are with widget builder, but easy enough to tweak standard music widget and root it toward Arc.