I too (like lots of people on here) run Roon on a Mac Mini and have my local music stored on a NAS drive. In answer to your question, it kinda depends on where you MacMini is and how you intend to use it - e.g. is it a headless server sat in a cupboard somewhere, or do you have it connected to say your TV and/or entertainment system, or to an amp and want to also use it to play music directly from it?
Have a look at this page which explains the functions of each of the elements of the Roon software - Server, Remote and Bridge - and their functions here
In my case the MacMini is in a server cupboard, so I don’t play music directly from its audio jack or USB sockets. The local copies of my music are stored on a QNAP NAS drive, so Roon Server on the MacMini is pointed to the shared folder on the QNAP. I also have a Qobuz subscription (which is fantastic) and so Roon pulls tracks and playlists from this source together with my local music and presents it as one big ‘Library’ (one of the big reasons I got Roon).
Playing the music is controlled by any of the iPhones, iPads, or other Macs around the house using Roon Remote, but they also can output music directly (headphone jacks or via USB) as well as directing the music output to other devices which are Roon endpoints only - like my Sonos players (which worked without having to do anything to them, other than simply enabling them in Roon settings), or on my Chord Poly/Mojo, which either outputs to headphones or active speakers (so it’s flexible).
So yes, it is absolutely possible and easy to do what you’re after, as well as expand your system if you want in many and varied ways. Have you already got your NAS and set up your music files on it? If you need specific help in this regard, please let us know which NAS and how you’ve got that connected to your local network. It might help also if you give an indication of your general level of competence with IT and networking so instructions are pitched accordingly.
Otherwise, if you’ve already set up a working shared folder on your NAS with your music on, all you need is the network path to this, and then insert it in the Roon menu: Settings > Storage page. The path should look something like \‘Network Name of NAS’‘Folder Name’ and you would need the user name and password for your NAS/shared folder (assuming you’ve set one).
If you use Tidal or Qobuz, add this in the Roon menu: Settings > Services.
Then set up your music output / endpoints in the Roon menu: Settings > Audio where you can enable output of audio on your iPad too if you want as well as your Naim streamer. No idea which Naim streamer you have. Is is certified as ‘Roon Ready’? If so and it’s connected to your network, it should be automatically detected and show up in the Audio menu, and you just need to enable it. There is a list of supported devices including the ‘RoonReady’ ones here
Sorry for the long post - hopefully this helps