Roman numerals follows the history of ancient Rome itself from its early stages at the Latin Palatine Hill in 8th and 9th century BC to its fall in the 2nd Century AD from civil war, plague, civil apathy and the rise of Christianity and Northern European powers.
“The Roman Empire had inspirational, industrious and intellectual beginnings. Emperor Domitianus, Aristotle, Aristarchus, Eratosthenes, Euclid and Archamedes helped to build Rome into an ancient power, developing sophisticated intellectual and mathematical skills to build the Colosseum, Constantine's Arch, Pantheon, Roman Baths and Civil society. However, their number system was flawed, it had no zero (0), and no single method for counting above several thousand units, (lines were often placed over numerals to indicate multiples of their value).”
Roman numerals were used to record numbers in stone, art and coins. However that was a long time ago, these days they are used for list items, chapter headings, copyright dates and to mark film sequels such as the Star Wars films.
Roman numerals are also used on clock and watch faces. If you have seen a clock with Roman numbers, you may have realised that the number four is written as IIII instead of IV, this is because it adds symmetry to the clock face – although I don’t really think it adds symmetry at all. Numerals are often used to show the time on sundials too.
You can see a pretty long list of Roman Numerals here. It goes from 1 to 2016, and don’t ask why it stops at that number, but yeah.
Oh and just a random fact here for you: This year (2009) in Roman numerals is MMIX.