A wind turbine rotor blade assembly includes a rotor blade having a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root. An edge extension is attached along either or both of the leading edge or trailing edge in a generally span-wise direction from adjacent the root towards the blade tip, with the edge extension having a contoured outer surface that defines a generally continuous aerodynamic surface. The edge extension has a terminal end that is spaced from root. A curtain is attached to the edge extension and extends in a span-wise direction from the terminal end t to the root. The curtain is formed from a pliant, flexible material that accommodates connection of the root to a rotor hub, as well as pitch movement of the rotor blade relative to the hub.