[rhelz]

Fun fact: The romans had abacuses (abaci?), which represent a positional number system--including a representation for zero. A Roman abacus would have beads arranged for both decimal (base 10) and dozenal (base 12) calculations--because some of their measures, e.g. 12 ounces to a point, were in base 12 much like the metric system is base 10-centric today. (the wiki article "Roman Abacus" has some nice pictures.)

So yah, Hero of Alexandria would not have had to even make any conceptual leaps like inventing positional number systems. The abacus he already had in his pocket would have been all he would have needed to get him started in the right direction.