Do you feel that drinking water from rooves is safe? I'm also interested in if we can put it on edibles. I'm also interested in the difference between cedar, slate, composition, clay and metal.
There are many people who collect rainwater for drinking water. I live on an island, and while we seem to have lots of water, smaller islands nearby are always short of water. There is a long history of collecting rainwater to drink.
Of course, lots of people collect rainwater for shampooing the hair, because it is soft, and when collected properly, clean.
Not all roof materials are suitable to collect drinking water. My favourite roofing anyway is metal roofing.
To keep cisterns clean, the first rainfall in a long time is allowed to rinse off the roof and discarded. Only when the rainwater is running clear will a valve be opened to lead to the water tank or cistern. It's all worked out...
Modern islanders use food grade tanks and pressure tanks to provide "nearly normal" service.