but it depends on the look your going for. sure you can go for a bump may, but if you're gonna do that your best off doing displacement map, then you get more realistic light rays and shadows.
I see what gster is saying bout geometry, but whats a few roof tiles, when the natural looking light gives it a much more real effect.
those who succeed are only the failures that never gave up.
https://www.vimeo.com/7080130