Thermal discomfort inside building is due to outside climate, especially by excessive solar radiation during summer or by temperature drop during a cold season. The use of phase change materials (PCMs) can reduce this effect by storing heat transmitted by sensible and latent heat. This ensures good situation of thermal comfort throughout the year. In this work, thermal behavior of two roofing systems is studied. One roof that is taken as reference is constituted by usual materials in building. In the second, two PCMs are inserted according to three configurations. The objective of the study is to assess incorporation effect of two PCMs within reference roof and to evaluate the optimum locations to reduce the energy consumption of air-conditioned room. A monodimensional numerical model, validated analytically and experimentally, is used to carry out a parametric analysis to determine the characteristics of the PCMs to be used and their optimal location within the reference roof regardless of the external climate effect. Numerical calculations are performed for three configurations of roof with swapping PCMs. Results show that insertion of PCMs in the roof provides the best energy consumption saving regardless of annual climate change. Reduction in energy consumption of an air-conditioned room depends on the combination of PCMs, their mutual thicknesses, and thermal comfort level.