The work presented in this paper is part of a comprehensive research effort aimed at understanding the influence of flow unsteadiness on leading edge cavitation. Pressure measurements are made on the suction side of an oscillating hydrofoil in the High-Speed Cavitation Tunnel. Leading edge roughness effects are investigated for both cases of fixed and oscillating hydrofoils. The cavity that detaches on the rough leading edge is thicker while its length is approximately the same as for the smooth configuration. Pressure fluctuations in the cavity closure region are higher for the rough configuration. It is observed that the cavity detaching on the smooth leading edge at fixed incidence can completely vanish when the hydrofoil oscillates.