The files have to come from somewhere. I was active in “computer audio” about when it started. I have a medium sized collection of computer files. These were ripped from CDs, and more recently purchased from various websites.
Starting from Zero, streaming from online services works just great, and is wonderful for trying out new music. Some of the services are very good at extrapolation from a starting song/artist I usually start with a known album, and let Roon extrapolate until it gets too weird..
If you have an Amazon Prime account, Prime Music has good offerings, but a pretty basic service. Apple Music is better in some ways.
Spotify is the young peopleÂ’s streaming king. My wife uses this service, as she is into alternative music, where IÂ’m more classic rock, and electronic.
The HiRez twins are Qobuz, and Tidal. Both are good, with slight differences in perspective.
Spotify, and Tidal have a “Connect” service which simplifies use with some streamers.