When entering roman numerals on a mobile keyboard, the first character is often capitalised. Usually, this is wrong and lowercase is far more common.

Either figure out if an input can be set to "lowercase" (try autocapitalize=off and/or treat first-letter capitalised roman numerals as lowercase (though this will not help "i" or "v" etc).

If the latter, may also make sense to allow conversion of a single "I" etc to "i", if joined to a later, consistent lowercase range.