In recent years, increasing of the non-dispatchable resources has posed serious challenges to day-ahead generation scheduling of the power system. Since these resources are random in nature, the issue of flexibility to cover the uncertainty and variability of those has become an important research topic. Therefore, having flexible resources to cover changes in the generation of this resources during operation can play an important role in eliminating node imbalances, system reliability, providing the required flexible ramping reserve and reducing system operating costs. Among these flexible sources, we can mention fast-response dispatchable generation units such as gas units and combined cycle units. Therefore, in this paper, a mixed-integer two-stage and tri-level adaptive robust optimization has been used, which is solved by column-and-constraint generation decomposition-based algorithm in order to jointly clearing the energy and ramping reserve with the presence of fast response and flexible resources. The simulation results show the efficacy of the proposed model.