If you go with Roon, I would just stick with Airplay for everything. The Roon Airplay features are first rate and probably the best on the market, other than maybe Airfoil. For the NAS route, many of them use their own software. Synology, for example, has Airplay built into most of their NAS if you use their DS Audio app. Of course, apps like Filebrowser can simply access hard drives plugged into your router and you can Airplay from the app using an iPhone or iPad. The main downside to Airplay is it plays everything at 16/44.1 resolution no matter what it is fed. It is bit perfect with that bit rate, though.