The benefits of retrofitting existing buildings with vegetated roofs are environmental, economic and social. Economic benefits include lower construction costs, lower running costs, and reduced costs of borrowing whilst the social gains include retention of familiar landmarks, and cultural capital. Environmental gains include retention of embodied carbon, and the re-use of existing materials. The environmental benefits are improved thermal performance and reduced heat loss and heat gain in buildings. This can lead to reduced operational energy costs for owners and tenants, providing economic benefits. However, the environmental social and economic gains are not perceived sufficient to persuade many owners to retrofit green roofs. Social, psychological and therapeutic gains occur when the roof is visible to users and is used for social interaction and relaxation. As an alternative food production system, green roofs could promote a shorter food supply chain, contribute to healthier communities and create local jobs and notably reduce the carbon footprints of food production. A little explored environmental gain in Sydney is the retrofit of roofs for urban food production. No empirical research has been conducted into the plant species best suited to urban food production, including native food plants, and the optimum substrate composition and depth, required to suit the NSW climate. The barriers and opportunities for urban food production in a high-density urban environment also require investigation.