At the Passive House class Katrin said that the house where she lived in Germany had a very old concrete tile roof. The tiles were cast at the site using a mold. She said that traditionally, the builder would cast a stack of extra tiles and put them in the attic along with a mold so that future owners could cast replacements.
We also watched a movie of a new passivhaus being built there. They used concrete tiles with lugs underneath. The lugs rested on 2×2 nailing strips attached to the roof sheathing. There weren’t any fasteners. She said the tiles interlocked some how, but other than that, gravity was all that kept them in place.
I found an aluminum mold supplier in California: Kinetic Die Casting