Roller compacted concrete (RCC) displays large variability due to a range of factors including material properties and proportions, water content, construction procedures and site specific factors. Structural analysis of dams, built with RCC, are conducted with a single set of material properties. For assessing seismic performance, the mechanical properties of RCC like elasticity moduli and tensile strength are primarily important. The main purpose of this study is to evaluate the effect of variability of elastic moduli on the seismic assessment of RCC dams. The elasticity moduli affects the soil-structure-interaction behavior and coupling of the system with the foundation substantially. The effects of its variability are assessed with Monte Carlo analysis compiling samples of material properties in accordance with the monitored variability from a wide range of existing projects. The analyses are conducted utilizing frequency domain analysis including rigorous consideration of the radiation damping and reservoir-structure interaction. The seismic assessment was carried out using multiple ground motions in order to include different frequency contents of motions and associated effects coupled with system variability. The tensile stresses on the systems, and their dependence on the system elasticity moduli was investigated.