Roller blind, which comprises: two lateral guides (5) parallel to and side-by-side each other; a take-up roller around which a fabric (4) is windable that is susceptible of sliding between the lateral guides (5); a transverse bar (6) fixed to the fabric (4) and extended between two lateral terminations (22) slidably engaged with the corresponding lateral guides (5); two first magnetic coupling elements (25) each fixed to the corresponding lateral guide (5); two second magnetic coupling elements (26), each of which fixed to the corresponding lateral termination (22) of the transverse bar (6) and engageable via magnetic attraction with the corresponding first magnetic coupling element (25) in order to retain the transverse bar (6) in closed position. Each magnetic coupling element (25, 26) comprises at least one pair of magnets (25A, 25B; 26A, 26B) with opposite polarity with respect to each other.