This paper presents the results of a study on the effect of truck configurations on the roll stability of commercial trucks in roundabouts that are commonly used in urban settings with increasing frequency. The special geometric layout of roundabouts can increase the risk of rollover in high-CG vehicles, even at low speeds. Relatively few in-depth studies have been conducted on rollover stability of commercial trucks in roundabouts. This study uses a commercially available software, TruckSim®, to perform simulations on four truck configurations, including a single-unit truck, a WB-67 semi-truck, the combination of a tractor with double 28-ft trailers, and the combination of a tractor with double 40-ft trailers. A single-lane and multilane roundabout are modeled, both with a truck apron. Three travel movements through the roundabouts are considered, including right turn, through-movement, and left turn. Different paths followed by trucks to perform through-movement or left turns are simulated. The simulation results indicate that (1) traveling on a truck apron increases the risk of rollover, (2) different movements and paths result in different dynamic responses, and (3) in general, the single-unit truck has the highest roll stability, followed by the combination of a tractor with double 28-ft trailers, whereas the WB-67 semi-truck and the combination of a tractor with double 40-ft trailers pose a higher risk of rollover than the other two.