From Roon 1.7 Is Live!:
Album Screen Improvements
This release also includes 2 changes on the album screen.
First, multi-disc sets up to 200 tracks will now get a new All Tracks tab. This view will allow you to view the entire album in a single list, which should ensure better presentation of multi-part works that span multiple discs.
Secondly, we added a new display setting. Going forward track numbers will be hidden on the album page by default, although it is possible to toggle them back on using the new setting