The forum is dragging it’s feet right now, so I can’t find the exact post, but the details are either in this thread or this one. Long story short, you need to edit one of the ui_atlas files in the Resources folder (inside the Roon app). There seems to be some variance between Mac and PC in terms of exactly which file you need to edit (as you’ll see when you read the right thread).
As an aside, I can’t tell you how happy I was when I got rid of the round artist images. It’s a small thing, and most definitely a first world issue, but who came up with that idea?