Plywood or other material to roof (Newtongrange, EH22)

I built this bin shed but the wood you see placed on top isn't enough to cover the whole roof, I am looking at leftover plywood or other material to make a roof. Planks, laminate flooring, plastic panels, wetwall panels, anything big enough to cover it, I have excluded tarpaulins because they get shredded with the strong winds we get.