Yeah, there are specific formuli for various metals, alloys, hardnesses, ductility, etc. I think the model people also do the same by putting several flat sheets from cans in an oven and simply run a clean cycle. This will take the work hardening (from forming the can) out of it and return it to very soft maliable heavy duty foil. As was mentioned, the same will happen once it is on the pot, anyway. It is MUCH easier to work with, folding, bending, even stretching, than leaving any work hardened tensions in the metal.
The same thing happens when I make the bottoms on the ExPots. I anneal them, then retool the bottom with a half dozen deeper ripples. Well worth the 15% increase in performance and it can be used on ANY stove, not just a caldera cone. The bottom again becomes harder due to the tooling work applied, it does not stay soft.
This is also why bending something till it breaks usually works. The compression/tension of bending causes the metal to become brittle. After three or more back and forth, it breaks, but the actual edge will be quite hard. Copper can be pounded till it achieves a good metalic density. It makes a fair to good knife, actually. But, like any tooled metal, heating it will reset the molecules, softening it again. I think the Egytians used copper stone cutting tools for statuary made by working raw copper. I believe forming sheets, as they did to make old tin or copper ceilings also causes the stretched metal to be stronger than unworked metal. Drawing metal works because the finer wire, after pulling, is stronger than the origonal. Heat again, is used to anneal it, or reset the molecules. Anyway, there are a LOT of examples. (I made a few celing tile forms for a restoration project when I was in my 20's and spent some time looking stuff up, BW: before web. We used copper sheets and painted them.)
For just a couple pieces of roof flashing, rolling is the same as drawing only limited to a couple dimensions, I would run them over a stove burner till they start browning. Once they have reached that heat, they should be quite wimpy. You can go further, but you risk melting it. Try a couple scraps. It only takes a couple minutes, likely less, over a methane or propane blow torch flame. MAP gas will be too hot, more than likely.