Click here and scroll down to the section headed 'Zero'. There you will see it claimed that the only recorded use of 'N' for 'nullae/zero' occurred in England in the 8th century, used by the Venerable Bede or one of his monks. This is long after the Roman Era, even though Latin was still a lingua franca in religious and other educated circles.
The big differences between Roman and Arabic numerals (the ones we use today) are that Romans didn't have a symbol for zero because there is no need for zero.
For evidence of this, look at the number 10 on a watch or clock face that has roman numerals.