The roller blind is for use in connection with roof windows mounted in pitched roofs and comprises a preferably spring-loaded roller tube (1) which is mountable at the top of the frame or sash structure of the window and a flexible roller blind cloth (2) rolled up thereon as well as an arrangement for retaining the roller blind cloth (2) when rolled out against the spring-load on the roller tube (1) at least in a fully rolled-out condition of the roller blind cloth (2), in which the roller blind cloth (2) in at least a comparatively narrow, ribbon-shaped zone (4) in parallel with the rollertuber (1) is designed for fastening an edge portion of an additional cloth (3) when the roller blind cloth (2) is rolled out, will hang freely down therefrom and when the roller blind is rolled up follow the roller blind cloth (2) during its rolling up on the roller tube (1).