The Roman numeric system revolved around the use of letters to represent numbers.
You may notice that the Roman numeric system did not cater for zero. This left it at a severe disadvantage to the Arabic system when monetary calculations needed to be done.
One possible reason why the Romans had not discovered zero as a concept is that their mathematics was mainly concerned with geometry, therefore always dealing in values above 0. Another advantage the arabic system had over the Roman system is that there are fewer figures needed, since the presence of a zero allows one to start again at 10, 20...90, 100 etc. This makes the arabic system far more suitable for calculations.
The Roman numeric system can still be seen in use at the end of films, however, to denote the year in which it was made. Also, Roman numerals in their lower case forms are sometimes used for numbering lists in books.