ᐅ Roof insulation using universal insulation boards combined with OSB panels?

Hello,
we are currently building a new house and planning to do the roof insulation ourselves.
The house will have two full floors plus the roof (urban villa with a hip roof).
The attic will be an unheated space and is intended mainly for storage, so we want to keep the effort as low as possible but without cutting corners!
The plan was to lay a universal insulation board on the concrete ceiling (200 mm (8 inches)) and then install 12 mm (½ inch) OSB 3 boards on top. This seemed like the most affordable and simple solution for the attic to me.
However, I have often read that installing OSB boards this way can lead to mold issues. Can you confirm this, and if so, is there an alternative to OSB boards?
Thanks in advance for your help!

Best regards

We were also advised to use tongue and groove spruce boards, since OSB is not very vapor permeable – although we have no idea if that might be different with a concrete ceiling.