Why? Is there any base 10 value which cannot be converted into a base 12 value or vice versa? If not, it's irrelevant which one you use. I believe that Roman numerals had limitations in regards to decimals and fractions, so it's not a relevant comparison.
The limitation of the Roman numeral systems was the lack of a zero. Roman arithmetic was a nightmare. It really never advanced beyond a counting on one's fingers level, and basically the numerals I, II, III, IV, and V, are simple representations of groups of fingers.
The lack of easy division and multiplication, which makes fractions even more difficult, created real problems when it came to tax collection. There was no such thing as a tax bracket or a marginal tax rate. The governor of a province was given an amount to collect. Any surplus was his to keep. The system extended down to local tax collectors. It was the retail level tax collectors who took the brunt of this system. Taxes had to be remitted in coin. The governor did not take pigs. In a cash poor society, this meant the tax collector might demand all the cash in the house. He was seen as thief who operated in daylight. With no fractions or percentages, the tax rate was basically, "What have you got?"