Why paint a galvanized roof? The question is of course interesting, but the answer is very prosaic — the thing is that after 10-15 years, galvanizing loses its property, but the paint at this moment can definitely be very useful. The roof at this moment is necessarily painted. Of course, the best option is to paint a new galvanized roof, and by itself simple paint is not suitable for this, adhesion should be even more than in colors used with conventional metals.