Roman Numerals

Roman Numerals did serve a useful purpose in that they allowed a new development in the Roman alphabet, two new letters U and J.

In the tenth century V differentiated into U and V, and in the 15th century I differentiated into I and J. V and J, the consonantal forms were used at the beginning of words and U and I, the vocalic sounds were used in medial position. (Isaac Taylor, The Alphabet ii p. 72)

The addition of new letters into the Latin alphabet was possible since, even though the letters of the alphabet had a fixed order, they did not have a fixed value. The addition of new letters to the alphabet did not alter mathematical notation. Roman numerals are not an alphabet derived system, regardless of what they look like.

In contrast, the Greek and Hebrew alphabets have not changed in 2000 years. The Greek alphabet did lose one letter in the mists of antiquity, the digamma, which occurred in 6th position and corresponded to the vav in Hebrew. That has since been replaced with the stigma, a letter used only for the number 6, and not included in the alphabet. However, it serves to ensure that the Greek letters retain their original numerical value.

The use of the alphabet as a numbering system provided stability or rigidity, depending on how you look at it, to the Greek and Hebrew alphabets. The Roman numeral system on the other hand differentiated the numerical system from the writing system and allowed the Roman alphabet greater flexibility. They all were base 10 - so no difference there.