Photo caption: "Two dodecahedra and an icosahedron on display in the Rheinisches Landesmuseum Bonn, Germany."
A Roman dodecahedron or Gallo-Roman dodecahedron is a small hollow object made of copper alloy which has been cast into a regular dodecahedral shape: twelve flat pentagonal faces, each face having a circular hole of varying diameter in the middle, the holes connecting to the hollow center. Roman dodecahedra date from the 2nd to 4th centuries AD and their purpose remains unknown. They rarely show signs of wear, and do not have any inscribed numbers or letters.
They were probably used for DnD before Romans discovered numbers; they'd get in an encounter, roll one of these and then point to the top facing section and tell the Coliseum Master "I got one of those". I'd imagine they were probably really eager to finally find numbers to make the whole process much easier.
That or they were still trying to discover lameness; they'd put them on the front doorstep of someone they disliked and it was the starting point of the phrase "you've just been served" except they'd be like "you've just been diced".