We introduce a new overlay network named ROSA1 . Overlay networks offer a way to bypass the routing constraints of the underlying network. ROSA used this overlay network property to offer a resilient routing to critical applications. Unlike other overlay networks dealing with the routing resilience issue, we oriented our research towards building a robust overlay network topology instead of a robust routing function. We tried to maintain a path between any pairs of nodes of the network. The routing resilience is obtained by forcing nodes to choose and modify dynamically their neighbors set according to the ROSA protocol. Moreover, ROSA is highly scalable.