In this paper, we reviewed three types of novel roofing systems which can reduce building thermal loads: cool roof, green roof, and phase change material (PCM) roof. Cool roofs are designed to keep the roof cool by reflecting the incident solar radiation away from the building roof and radiating the stored heat away at night. Green roof, also called eco-roof, covered by vegetation, utilizes the thermal insulation provided by the soil and evapo-transpiration to keep the roof cool under the sun. PCM roofs employ phase change material with high latent heat of fusion in the roofs. PCM roofs are able to absorb large amount of heat at demand peak when PCM changes its phase, so that the heat from outdoor is stored in the PCM rather than flows into indoor space. The effort in the paper has compared the key parameters of each of the systems, thermal analysis methodologies, and the energy savings due to each of them with reference cases, in addition, we provide a comprehensive thermal analysis method applied in novel roof systems and a guide to design proper novel roofing system for a given climate and building types.