The brief answer is that you can substitute semi rigid mineral wool panels for rigid foam in any roof assembly that requires rigid foam.
Roxul on roof.
Single ply roof insulation.
Rockwool multifix is a mineral fiberglass faced stone wool product that can be installed under many single ply membranes.
Known as comfortboard is this insulation has impressed us with its green virtues versatility and price.
An underlayment will be installed over the insulation and overhang and then the metal roof is installed directly on top of the underlayment.
Single ply roof systems can provide an easy to install seamless roof assembly.
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.
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.