iReal Pro can print a chart in scale numbers instead of chord names, in the spirit of the Nashville Number System, so it reads in any key.

 

Open Chord Chart Settings (the Aa button on iPhone, iPad, and Mac, or A on Android) and choose Number Notation from the Font list. On Windows, set the Font in Settings. Roman numerals are on the same list.

 

For more, see Change how your chord chart looks on the iReal Pro website.