Modern roundabouts are developed to increase the traffic capacity and decrease the traffic delay. They are popular around the world and are becoming common in Canada and the United States. A great design of a roundabout is to achieve the minimum delay. According to the research papers regarding the delay at roundabouts, it is expected the vehicle delay, the stop ratio at various traffic volumes, and the level of saturation of roundabouts are smaller than the amount of similar parameters on un-signalized intersections. The purpose of this thesis is clarification and measurement of the geometric parameters through the RODEL software to depict their influence on the sensitivity of roundabout delay. This study has been done through creation and analysis of numerous tables and graphs for various traffic volumes and peak periods. Furthermore, the required accuracy of each parameter in estimating delay of a planned roundabout is determined.The outcome of this analysis indicates the effects of the geometric parameters on the roundabout delay. While the Half Width, Entry Width, and Flare Length have the greatest influence on the delay, the Entry Radius, Entry Angle (PHI), and Inscribed Circle Diameter have the least influence.