Thought I'd share some additional precedent on roof gardens that I've researched...

Roof gardens are believed to have been used in ancient times as a communal space, an extra room to be used for an occasional visitor.  In these earthen homes, which were built in the warm climates of ancient Mesopotamia and Egypt there is evidence of roof gardens above the house.  Many times basic furnishings such as a bed, table, chair, and candle were set up for the occasional visitor. Interestingly, even downright surprising is the interpretation by some of roof gardens in the Holy Scripture.  In 2 Kings 4:10 “Please, let us make a little walled upper chamber and let us set a bed for him there, and a table and a chair and a lamp stand; and it shall be, when he comes to us, that he can turn in there.”

While the psychological benefits of a hospital roof garden for patients are known to be beneficial, the physical and medicinal benefits of being several stories up above the city streets are thought to have validity. Tenement buildings in Brooklyn during the turn of the century (known as “wage earners’ homes”) were designed in some cases with roof gardens for the “general good health” of laborers.1 
Hospital Roof used for the benefit of chidren

“The tuberculosis roof camp was another development in the early 20th century.  Sufferers from ‘the malady,’ were invited to spend the day in these camps.” 2    Some of the press and medical field called for these tuberculosis “light” hospitals to be on the roof of every large apartment building in poor neighborhoods.  There would be playground areas and covered areas for beds.  The belief was that you would quarantine the already sick from healthy children and provide them with a better chance of recovery in this “purer atmosphere.” 2

The restorative benefits of time spent in a roof garden are well documented in the American Journal of Nursing.  In 1935 the local garden club helped to create vegetable and flower gardens atop the Children’s Hospital of Akron, Ohio, “with a wish that blessings of health be restored to each little one entrusted here.”3
Illustration for nursing building with roof garden
According to Theodore Koch in “A Book of Carnegie Libraries”, ninety years ago along the Lower East Side of Manhattan, Public Libraries created open-air reading rooms on their roofs, complete with tables, chairs, flower boxes, awnings and lighting for late-night readers.

 Young girl reading @ roof garden library circa 1910

1.Fortmeyer, Erik, “Were There Ever Roof Gardens in Boerum Hill?”
2  Shaw, Albert, (editor) American Review of Reviews Vol XLII, July-Dec 1910: Ann Arbor: U of Michigan Press 1910
3 Chambers, Marion, “A Roof Garden”, The American Journal of Nursing, Vol 35, No. 4 (April 1935) pp. 315-318