I know this topic is old. but I saw something on the roman dodecahedron today and had to put my 2 cents in someplace on the internet.
Idea 1. since it was found in with coins a few times it could be a way to measure currency, I saw different dodecahedrons. some looked to have small holes. those could be to size and find value to gems.
idea 2. this reminded me immediately of a toy my great grandmother had for me to play with when I would go to her house. it was wooden though and had a thin rope with a wooden stick on the end. I could then tread the string through different holes. since the roman dodecahedron has different size holes. it could have been a puzzle toy. where a thin rope had different size balls and you would have to thread the string through in the right order or it would not get through all the way as they would not fit unless in the correct order.