It’s definitely been requested before. If you search, you’ll see lots of comments about requests for improvement of box set handling, and being able to see the titles of the discs is one of the requests.
One workaround is to put in each as a separate title, whatever the original disc was. This of course doesn’t help with any bonus discs, outtake discs, what have you.
I’d like to say Roon is working on it but they’ve been pretty silent about it for quite some time. The team has been more focused on partnerships - Qobuz, MQA, hardware endpoints - than its interface for the past year or so. That is not to say there haven’t been some cool interface stuff in their latest releases, but the focus on integrations and partnerships is pretty clear.