I use the ROONALBUMTAG tag to show the DRi value in Roon.
To do this first I find the DRi value of the album by mesureing it using a software: MAAT DROffline MkII You can also find the vaule in the DR database https://dr.loudness-war.info/ if you know which version of the album you have.
Then I use an external tagging program. Any will do. I use Mp3tag - the universal Tag Editor (ID3v2, MP4, OGG, FLAC, ...) Here I add the tag ROONALBUMTAG to the album files and I give them the DRi value I messured (or found) in the first step.
Roon then automatically updates the album info and show the DRi value as a tag like here:
Its not complicated if you are familiar with tagging but it is time consuming. There is a feature request to make Roon do this automatically that you can vote for: Select "R128" or "Crest Factor" DR
You can read more about ROONALBUMTAG and ROONTRACKTAG her: https://help.roonlabs.com/portal/en/kb/articles/tags#ROONALBUMTAG__ROONTRACKTAG
Its a great way to organize and get info into Roon.