Unfortunately, installing a white roof isn’t quite as easy as opening a can of paint. Most roofing material manufacturers (including manufacturers of asphalt shingles) will not extend their warranties to roofs that have been painted or covered in some way. Many low-sloped (i.e. almost flat) roofs are covered with elastomeric coatings that are specifically designed to withstand weathering. These coatings can be painted on, which is why you see pictures of people painting their roofs with rollers.