Roofers are skilled tradesmen who specialize in repairing, replacing, and installing the roofs of commercial buildings. They work at the edges of the roof like the corners and pitches. Other roofers work from the center of a building extending up the sides and ceiling. A roofer may be involved in any part of a building's roof from roofing to cleaning. The roofer's task depends on the size of the building, its structure, the type of roof, and the needs of the roofers.