OpenType font shaping is shockingly powerful ([e.g.](https://blog.janestreet.com/commas-in-big-numbers-everywhere/) https://blog.janestreet.com/commas-in-big-nu

OpenType font shaping is shockingly powerful ([e.g.](https://blog.janestreet.com/commas-in-big-numbers-everywhere/) https://blog.janestreet.com/commas-in-big-numbers-everywhere...), so I'd be surprised if someone hasn't made a Roman numeral font already.