Roof stone tiles. How to fasten them?
You can buy special metal brackets for roof tiles:



Most of the roofs I have seen have used nails, and only in certain places, relying for the most part on the friction and weight of the roof tiles to hold them in place.  Whether brackets are required depends on wind speed, wind direction, subroof type, roof angle, roof shape, height, and other factors.  

Regardless of whether you use brackets, nails, or screws, they must be stainless, galvanized, or otherwise protected from corrosion.  Nails must have ring-threaded shanks.

(Source: manufacturer's instructions for various roof tiles sold in Norway.  Check your local building codes and the instructions provided by the manufacturer of your roof tiles.)