Will it ever be possible to use Roon in offline mode, to play files saved locally on the phone? This would be a killer feature as I often listen to music offline (on trains, in the metro, when flying, etc.) or anyway away from home. There was a similar request in Oct 2017 but no news on that front.
Take a look at the following article which explains how Roon works. You’ll then understand that offline isn’t feasible since all the heavy lifting is done by the core. However, mobile Roon is discussed in the forum–see feature requests.