There is a green roof on the Washington University Campus on the South 40:

“An environmentally friendly “green roof” — containing grass, native plants and approximately 110,000 pounds of soil — opened last week at the South 40 House on the university’s Danforth Campus. The roof shelters a loading dock, kitchen and other areas of the South 40 House’s southern lower level.

The 10,150-square-foot green roof connects seamlessly with the lawn to the east near Liggett and Koenig students residences, creating a large grassy area that also features paths and benches.”