The reason I mention Rome is that I learned this weekend that those Romans... they were AD&D geeks. And for just under $20K you can buy one of their 20-sided dice.
A ROMAN GLASS GAMING DIECan't you just imagine Ceaser yelling "Roll the dice to see if I'm getting drunk!"
Circa 2nd Century A.D.
Deep blue-green in color, the large twenty-sided die incised with a distinct symbol on each of its faces
2 1/16 in. (5.2 cm.) wide
Several polyhedra in various materials with similar symbols are known from the Roman period. Modern scholarship has not yet established the game for which these dice were used.