A Google search identifies metal sandwich roofing panels from India and China, but not from US manufacturers. I want to reroof over a shingle roof with metal roofing and would like to add insulation at same time. These panels were used in my Iraq reconstruction projects -- but are they too high tech for US?

I would seriously doubt it being too high tech.More like too costly for what it would deliver.Overkill for the USA needs(except in some desert regions)or lastly,because they might not pass the testing required for the US.(politics included)

If you want to add insulation under a new metal roof there are a few options I know of right off hand.

One would be a product formerly known as ' Nail line ' ,it was a sandwiched polyisocyanurate panel with OSB on the top and bottom.Thickness could be determined by needs.(R7 per inch)

You could also use the poly as separate individual panels installed between the 2X framing you would apply for the new metal roof.

Out-gassing from this product has shown a certain amount of insulation value loss over the lifetime of it(Ours has lost perhaps 10-12% in 15 years)But I believe that most solid insulation's have this also.

Other than that,perhaps others can offer you further information on additional products.

KBC