This thread is going to kill me if I don't walk away. I'm the type that has to try to find the answers. Great question on no Roman numeral for zero so this is what the all knowing and all powerful internet says (romannumerals.org). I learned something today, I think I'll go home now.
"the Romans didn’t have a symbol for the number zero (0). Because Roman Numerals System was developed for mostly knowing the price of goods, and to trade. So, there was no need for a symbol to represent zero. Instead of the number zero, the word “nulla” (the Latin word meaning "none") was used by the Romans."