[jacobolus]

You can do long division just fine on a counting board, though it is unclear if people had developed something like the modern elementary school division algorithm 2000+ years ago.

We don’t really know much about people’s calculation algorithms, because they were an oral tradition not written down, and only a very small number of counting boards (e.g. made of marble) survived; others were presumably made of leather, wood, cloth, lines scratched in the dirt, ....

Japanese soroban experts handily beat westerners at doing division, in both speed and accuracy. There is no reason to believe that calculation experts of the ancient world would not have been comparably competent.

[WalterBright]

> You can do long division just fine on a counting board

I searched around a bit, and didn't find much of anything you could do with a counting board beyond division.

[mlyle]

Counting boards / the abacus are about as good as you get for calculating methods until mechanical calculators and logarithmic slide rules. So it's not really fair to say the Romans had a disadvantage here when no one had anything better. (Granted, the wire abacus was faster than counting boards / jetons).