I would like to propose that streaming has fundamentally changed music for the audiophile. It has been a complete paradigm shift. Ownership points you to a very limited library, and being confined to that library. My ownership is 4,000 albums. Something you could kind of keep in your head. Streaming opens you up to about one million albums. With a good streamer, depending on the rest of your system, the streamer can have higher quality than your CDs, stored files, or vinyl.
You can make the transition into a new Paradym with an old way of looking things. Then over time you are likely to discover that this is a different world. When you have basically access to all music, things change from locating the same old stuff to exploration. My habits completely changed over the first couple years of streaming once the sound quality was equal or better than CDs and vinyl.
So, first, I recommend putting a lot of effort into getting a very high quality streamer. Personally I prefer Aurrender at about any price point. I would not worry about taking your old files along and organizing them. Sure, throw them onto your streamer in case you lose your internet.
The Roon question is a good one. Great quality streamers have exploration and library tools. They will combine the stuff you own with stuff you find in streaming. Roon is a good exploration tool, but it is a hassle, cost money, may degrade the sound, and is really unnecessary. The functions provided with Aurrender are really adequate to help you navigate, explore, and collect new music (leave breadcrumbs to find what you liked).
If your personality is very anal retentive then a streamer that supports Roon is the way to go. But not a PC or MAC… a real high quality dedicated streamer.
My recommendation is to work on getting a world class streamer for your system… focusing on sound quality… then learn what the world of streaming is like.
I now primarily listen to music I have never heard before instead of the stuff I bought… everything I bought is already there. Sometimes I’ll locate an album I used to listen all the time and listen to earlier and later recordings by the group or adjacent groups. It is a truely incredible works of music and opportunity to explore.
Oh yes, you want to use the Qobuz service. Sound the best and the have over half a million high resolution albums… and that is growing every day… and for the cost of buying a new CD each month… what a deal!