A roller brush assembly comprises a roller and a brush set on the roller. The roller contains an interior cavity constituted by at least two barrel bodies. Each portion of the barrel body edge is serrated shaped, and the adjacent serrated-shaped portions of the barrel both form a blade slot for positioning the serrated-shaped blade, and the blade edge corresponds to the teeth on the serrated shaped edge. A driver unit is installed in the interior cavity to make the blade move along the roller axially to cut the wrapped in the tooth groove automatically when the roller brush is turned on and off.