ROCS: a robustly complete control synthesis tool for nonlinear dynamical systems. This paper presents ROCS, an algorithmic control synthesis tool for nonlinear dynamical systems. Different from other formal control synthesis tools, it guarantees to generate a control strategy with respect to a robustly realizable specification for a nonlinear system. At the core of ROCS is the interval branch-and-bound scheme with a precision control parameter that reflects the robustness of the realizability of the specification. It also supports multiple variable precision control parameters to achieve higher efficiency.