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Urban agriculture serves a growing and valuable market in today's food industry yet is challenged by the lack of available space in urban settings. Green roofs are proving not to only offer environmental benefits to buildings, but to also function as sites to grow produce. Adding fertilizer is important for plant health though fertilizer runoff and over application is a concern. Therefore, an evaluation of four Romaine lettuce cultivars (Lactuca sativa L.) comparing the use of three different fertilizers was conducted on the green roof of the Agriculture Building on the Southern Illinois University Carbondale campus in the fall of 2012 and 2013. The fertilizer treatments were OsmocoteTM (190,000 mg/kg N), Miracle GroTM (16,100 mg/kg N), and a control (no fertilizer). Supplemental water was applied though a drip tape irrigation system as needed. The lettuce cultivars evaluated were: ‘Parris Island Cos’, ‘Rouge d'Hiver’, ‘Rubens Baby’, and ‘Outredgeous’ Romaine lettuce. Results indicated that plant growth measurements of height and width, chlorophyll index, leaf mass and wet/dry weight were greater (P < 0.05) when OsmocoteTM and Miracle GroTM were used as a fertilizer source compared to the no fertilizer treatment. This study indicates that with supplemental nutrients, acceptable lettuce yields can be achieved in a three-inch extensive medium on a green roof. Results of this evaluation will contribute to the emerging interest in urban agriculture, specifically regarding lettuce production on extensive green roofs.