The fact that event-triggered control (ETC) often exhibits an improved performance-communication tradeoff over time-triggered control renders it especially useful for Networked Control Systems (NCSs). However, it has proven difficult to characterize the traffic produced by ETC a priori, making it hard to adequately dimension the communication system. Rollout ETC addresses this issue by using a triggering and control law that is implicitly defined by the solution to a receding-horizon optimal control problem (OCP), instead of an explicit one as in classical ETC. This allows to directly incorporate predefined constraints on the transmission traffic as well as on states and inputs. In this article, we examine the practically relevant case when output instead of state measurements are available for feedback, and measurements as well as the plant are subject to uncertainties. To address these challenges, we adapt methods from robust tube-based model predictive control and propose three different strategies to implement an error feedback in an NCSs setup, the applicability of which depends on the capabilities of the actuator. We establish recursive feasibility of the OCP, satisfaction of state and input constraints despite the uncertainties, and convergence. Finally, we illustrate our results in a numerical example.