Power
In general terms, roofers aren't that powerful. You're probably not going to hear the mayor of your town saying, "What we really need to do is find out what the roofing industry movers and shakers think about this." On the upside, though, you'll never have to worry about being called away from work to sit through a mayoral board meeting—which you'll probably be fine with.
This isn't to say roofers are powerless. Quite the opposite, in fact. Roofers have a lot of power over their customers because the roof is, obviously, a hugely important piece of a house. How quickly the roof can be finished determines how quickly a new house can be built. It's called getting the house "in the dry" for a good reason.
Who wants to be running electrical equipment, wires, or putting up sheet rock and insulation if it could rain all over and ruin it? That's a surefire way to singe your eyebrows off—or worse.
Because the roof is what protects the structure, roofers have power not only over how fast a house can be built, but how well it can be protected. Theoretically, you could ruin somebody's home by doing a shoddy job. That'd put you out of a job pretty fast, though, so maybe it'd be better to stick to that "quality work" philosophy.
When you use your power to protect peoples' homes, furnishings, and memories, they'll be grateful. Then they'll tell all their friends what a great roofer you are, and those friends will hire you. Strong customer service builds relationships to grow your roofing business, and that's the best kind of power you can have.