12 pentagons and 20 notches.
Print notches upright with brim.

My testprints are done with PETG.

Assembling is quit callenging. But the final dodecahedron is very stable.
fix always 3 sides with one notch gentely. When all done pusth the notches further in.

The Roman dodecahedron is a unsolver mystery. On my version all holes have the same diameter. On real ones they are all different.

https://en.wikipedia.org/wiki/Roman_dodecahedron 

I designed and printed this object a few years ago when I read the first time about it.