Roof mounted wind turbines represent the future outlook of wind energy generation in the urban environment. However, the urban environment is characterised by low wind speed and high levels of turbulence which has a negative effect on the performance of the current wind turbine systems i.e. horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT). These problems can be alleviated by mounting a novel cross axis wind turbine on rooftops of urban buildings to take advantage of the increased wind speed at the top of the roof. The roof mounted cross axis wind turbine (RMCAWT) is designed to operate by interacting with wind speed that is coming from both the horizontal and the vertical directions when mounted on the rooftop. The RMCAWT consists of three main vertical blades, & six horizontal blades arranged in a cross axis orientation. The wind flow on the building rooftop was investigated by using computational fluid dynamics (CFD) simulation software to ascertain the vertical component of the wind at the rooftop. The RMCAWT was tested on a vaulted rooftop and its performance was compared to a bare-CAWT (without rooftop) mounted on an equivalent height as the roof mounted CAWT under similar experimental conditions. The results obtained from the study showed that the RMCAWT outperformed the bare-CAWT. The coefficient of power (Cp) and rotational speed (RPM) of the RMCAWT increases by 37%, and 89% respectively compared to the bare-CAWT.