Hi Jonas,
The issue you describe should only happen if we’re not able to determine which tracks are part of each disc. The simplest way to fix this would be to edit the file tags so each disc is clearly identified as 1/2 and 2/2. You might also make sure each disc is in its own folder, titled “Disc 1” and Disc 2".
Once you’ve made these changes, Roon should recognize the changes and organize the discs properly. (Note that to pick up the tag changes, a restart may be required – this is fixed for our next release).
You might also read over @jeremiah’s post here about how to make sure multi-disc sets are imported and grouped properly. Let me know how it goes!