Roman numerals are well known. Although they are striking in a monumental kind of way they are a clumsy way to represent numbers. Roman numerals are often used to number rulers eg. Henry VIII, Louis XIV. They may used for copyright dates for films or for prefaces in book. Roman numerals on gravestones create an impression of dignity.
The Roman numbering system lives on in English, which still uses Latin roots to express numerical ideas eg. unilateral, duo, quadricep, septuagenarian, decade, milliliter.
The big differences between Roman and Arabic numerals (the ones we use today) are that Romans didn't have a symbol for 0, and that placement within a number can sometimes indicate subtraction rather than addition.
This program converts an Arabic integer number into its Roman number.