This package provides only two macros: \modromannumeral which writes the number given as argument in lower case roman numeral with a j instead of a i as the final letter of numbers greater than 1, and \modroman, which writes the value of a counter in the same way.

You use the first in the same way as the TeX primitive \romannumeral and the second as LaTeX command \roman. The default option is vpourv with which 5 is translated as v and option upourv with which the same 5 is given as u.