The convert(s, arabic) command converts a symbol or string s that represents a Roman numeral to an integer.

The format for Roman numerals is given on the convert/roman help page.

$\mathrm{convert}\left(\mathrm{XVI}\,\mathrm{arabic}\right)$

$16$

$\mathrm{convert}\left(\mathrm{MCXLVII}\,\mathrm{arabic}\right)$

$1147$

$\mathrm{convert}\left(''CI9CI9II''\,\mathrm{arabic}\right)$

$2002$