Where can one get sheets for their roof?

The answer is somewhat affected by the geographical location of the roof in question. Roof sheets are normally supplied through local business suppliers of roof sheeting. For example if a buyer was based in the United Kingdom then a company called Accord Steel Cladding would be able to supply the requested materials. Alternatively you can latch onto third-party knowledge through a local builder, they would be able to source sheet roofing through their own personal contacts and suppliers.