The record for the largest rooftop solar system in North America keeps falling. Two years ago, it was 3 megawatts at a warehouse serving GlaxoSmithKline in York County, Pennsylvania. Then it was a 5.38 megawatt system for Toys "R" Us in Flanders, New Jersey.
Now it is a 9 megawatt giant at the Gloucester Marine Terminal, again in New Jersey, close to the Walt Witman Bridge that connects the Garden state to Pennsylvania. http://cleantechnica.com/2012/04/07/largest-rooftop-solar-power-plant-in-north-america-formally-completed/. The link has an amazing photograph of the system, with the Philadelphia skyline in the background.
The 9 megawatt giant rooftop system covers 1.1 million square feet and will provide enough power for the equivalent of approximately 1400 homes. Records are made to be broken, but breaking the 9 megawatt mark for a rooftop solar system is not going to be easy.