I’m not sure why there’s always so much focus on purpose. People build objects of geometric fascination as art objects all the time. I agree with you that there need not be any religious significance here.
Worth looking at how the Romans themselves thought. They were incredibly superstitious, overbearingly and obsessively religious (this is Roman Catholicism's roots), they believed in magic and spirits, constantly consulted oracles, augury, and other signs to make important decisions, and key roles in the Roman government was run by people who were also priests, in the Republic and early Empire most civic functions were also religious, and after Caesar they regularly deified their leaders.
Given that this object was clearly precious to its owners (found in treasure hoards/graves), wasn't used as a tool where it would receive any wear, and no one discussed it at all, a cult object would make a great deal of sense. Perhaps Gallic Rome had a regional cult these are tied to. There's a massive number of other Roman ritual objects, magic tablet, amulets, curse tablets, and other religious ephemera, the Romans really loved their cults and rites, if you have an unknown Roman object that's conspicuously not spoken about like these things, that itself is a fair reason to suspect the object might be used in secret religious/cult rites.
"Its a cool object" doesn't quite explain its ubiquity, or the fact that they are almost identical looking despite which side of the globe their on. That suggests purpose to me.
Dodecahedrons are fundamental shapes. Thus universal. And also expected size would be pretty much same. In general symmetry is pleasant. So I would expect symmetric shapes to come up when people have enough time and resources to build them, even if they have no use.
I guess when future archeologist dig up our junk they'd believe we were an extremely religious society, with many superstitions and strange beliefs. /s
All it means is that the way the object was used has no relation to the functionality of the object itself.