This contribution presents a decentralized control strategy for the automation of roundabouts, in which autonomous vehicles are required to circulate without collisions and to safely interact with pedestrians. The inherent hierarchical controller incorporates a consensus-based auction algorithm, which allows vehicles to agree on a crossing order at each entry point of the roundabout. An on-board scenario-based model predictive controller avoids the occurrence of collisions with other vehicles and pedestrians, while optimizing performance metrics over time. We run stochastic simulations that confirm theoretical findings.