Here's a rooftop garden that's feeding about 10 families.
They are called Community Growers in Milwaukee, WI. They are operating as a CSA (Community Supported Agriculture) meaning they sell shares of the harvest on a subscription basis throughout the growing season. They even sell to the local health food store across the street.
Owner Erik Lindberg is on a mission: To grow organic vegetables and fruits in an urban environment, to promote local food production as an alternative to agri-business and corporate food distribution, to innovate new and better methods for urban farming, to provide leadership in urban farming and inspire others to grow their own food, to provide successful models of local business, to advise and coach other aspiring urban farmers, to install additional urban farms and gardens, and to green his city wherever he can.
Water is an issue because of the additional heat on the roof, and the lettuce may wilt early. But the rooftop tomatoes came up a week before all the land grown tomatoes! It's all a learning process.
Most important: this was previously useless space, now growing food.