I have created a font for use in producing Roman numeral analysis. The font is still in development, but it is at a stage where it is quite usable and can produce very nice results for most basic cases. Here are links to download it in Open Type (OTF) and TrueType (TTF) formats:
The font requires no special software support, so it works with pretty much any program that can use fonts. I have tested it with MuseScore and LibreOffice, and I assume it will work in any commercial alternatives to these free and open source applications.
To use the font, just install it normally (e.g., on Windows, double-click the download file then click the "Install" button in the dialog that appears), then select and use it normally in your program of choice.
For example, in MuseScore, you can can enter your analysis as lyrics or as staff text, and use the Inspector to select Campania as the font. You can then optionally hit the "Set as style" button (labelled "S") to make all text of that type use Campania. If you use lyrics, you can press Space to move to the next note while entering your analysis; if you use staff text, press Alt+Right.
Feel free to leave comments with any suggestions or problems you encounter using Campania. My plan is to collect feedback, make whatever improvements I can in response, and then post an update and make a bigger announcement.