Direct numerical simulation is performed on a 38.1% scale HIFiRE-5 forebody to study stationary crossflow instability. Computations use the US3D Navier-Stokes solver to simulate Mach 6 flow at Reynolds numbers of 8.1×106/m and 11.8×106/m, which are conditions used by quiet tunnel experiments at Purdue University. Distributed roughness with point-to-point height variation on the computational grid and maximum heights of 0.5-4.0 µm is used with the intent to emulate smooth-body transition and excite the naturally-occuring most unstable disturbance wavenumber. Disturbance growth rates and wavelength evolution are analyzed, and the effect of roughness height and forcing character is considered. A steady physical mechanism for the sharp increase in wall heat flux seen in both computations and experiment is introduced. Crossflow vortex coalescence is observed and a possible cause is discussed.