A roof ventilation assembly has a ridge framework corresponding to a vent on a roof, a top cover, front and rear panels and two baffler assemblies. The two baffler assemblies are respectively mounted on two sides of the ridge framework leaving two gaps between the baffler assemblies and the top cover. When heated air under the roof rises, the heated air goes through the vent and out of the slots. Therefore, the heated air can be expelled by the roof ventilation assembly cheaply and easily, without requiring maintenance and external power source.