Single ply roof insulation.
Roxul on roof.
The siding will also secure it.
An underlayment will be installed over the insulation and overhang and then the metal roof is installed directly on top of the underlayment.
A few washer nails hold the comfortboard in place.
The more extended answer is that while this approach is fairly common on flat commercial roofs especially in europe it is almost never done on sloped roofs especially in north america.
The walls are covered in two layers of 2 in thick rockwool.
The insulation planes with the roof overhang on the left.
The brief answer is that you can substitute semi rigid mineral wool panels for rigid foam in any roof assembly that requires rigid foam.
Made in canada by roxul comfortboard is one product in a line of stone wool products that combine the power of rock with the characteristics of insulation wool.