We use particle dynamics simulations to investigate the rheology of granular flows composed of regular octahedral particles in a rotating drum. We focus on the cascading regime and perform an extensive parametric study by varying drum size, particle size, rotation speed, and filling degree. Our simulations indicate that the passive layer undergoes quasistatic shearing and, in contrast to spherical particle flows, no sliding occurs at the drum wall due to the angular particle shape. A scaling parameter combining the Froude number, the ratio of drum to particle size, and the filling degree captures the kinematic and dynamic characteristics of the granular flow such as free surface shape, shear velocity, flow thickness, and inertial number. This scaling suggests simple linear correlations between free surface curvature, flow thickness, and inertial number. We also show that this scaling is fully consistent with the expected effects of increasing particle size.