Roller shutter for blackout effect of windows comprising a plurality of parallel laths (2, 71-83) constrained with respect to each other so that they can be wound up around a roller (3), to which the first one of said laths is constrained, characterized in that a portion of said laths is spaceable with respect to each other and a portion of said laths is not spaceable with respect to each other, said not spaceable laths (71-77) being the first ones starting from said roller (3), and in that said spaceable laths (78-83, 221-224) are constrained with respect to each other by means of "U" hooks (5,54,90) sliding inside slots (2203,2204) provided in the profile of said laths.