Techniques for performance measurement are an integral part of a revenue management (RM) system. The Revenue Opportunity Model (ROM) is a widely known method to measure revenue management performance. While adapting the ROM to recent developments of revenue management science - i.e. the advancement from leg-based to network-based RM controls and the recent transition from independent to dependent demand structures - the question of applicability and in particular the validity of the ROM have become increasingly important. In this thesis we model both independent and dependent demand structures in a network-based ROM and investigate its main properties. Furthermore, we consider different aspects of airline RM to make the application of the ROM possible in practice. We not only cover a disaggregation of the aggregated network ROM measures to single legs, but also to single RM components. In this thesis we therefore introduce a novel simulation-based approach to investigate the ROM properties particularly to measure its robustness against errors in the estimated unconstrained demand. The RM system used in the simulation environment reflects all main components and RM methods in use of a large network airline, particularly regarding state-of-the-art demand modeling and optimization models. The network-based ROM, both with independent and dependent demand, proves itself robust against errors in the estimated unconstrained demand for realistic input data with better robustness results for the ROM with independent demand. Moreover, a disaggregation of the ROM measures to single flight legs is possible. However, the ROM shows less robustness on a leg level. In addition, an approach to isolate the contribution of overbooking, upgrading and fare-mix from the overall success is introduced. In particular, the ROM measures for overbooking and upgrading prove themselves to be very robust.