Thanks @kayo, and welcome to Roon! By now, I’m a bit more familiar myself with Roon and digital music collections (a year ago I never used a computer, just played cd’s with my player). I also learnt that metadata indeed matters very much and had to go through a learning curve! But… slowly getting there! 
Koen,
I couldn’t agree more that “metadata indeed matters very much”, and I had to go thru a learning curve with managing it as well.
I have an Autonomic MMS-5A media server now for 3+ years, haven’t used it much since I got Roon. I record my CDs and purchase/install hi-res AIFF files, managed by iTunes…the Autonomic has a nifty app that mines the new adds to the iTunes library, identifies and syncs it from my Windows 10 machine to the MMS-5A. Once the files were over on the Autonomic, using the controller app, iTunes often times so messed up the metadata, artwork and grouping, I had to go thru my entire iTunes library and uncheck the “compilation” box, and had to go thru Amazon to download and override the album artwork.
I find that Roon is MUCH better at recognizing groupings and artwork, compared with iTunes.