Roller blind, which comprises: - a support frame intended to be fixed to a load-bearing element; - a take-up roller rotatably constrained to said support frame and having a rotation axis; - two lateral guides extended parallel to each other and side-by-side along respective first extension directions substantially orthogonal to the rotation axis of said take-up roller; each said lateral guide extended along the corresponding said first extension direction between a first end, positioned at said take-up roller, and an opposite second end; - a fabric extended between a first edge thereof fixed to said take-up roller and a second edge thereof, and susceptible of sliding between said lateral guides; - a transverse bar fixed to the second edge of said fabric and extended, along a second extension direction parallel to the rotation axis of said take-up roller, between two lateral ends thereof slidably engaged to the corresponding said lateral guides; said transverse bar being movable between an open position, in which said transverse bar is placed at the first ends of said lateral guides, and a closed position, in which said transverse bar is positioned at the second ends of said lateral guides; - at least one first magnetic coupling element, which is fixed to the second end of the corresponding said lateral guide; - at least one second magnetic coupling element, which is fixed to the corresponding lateral end of said transverse bar and, with said transverse bar arranged in said closed position, is engaged via magnetic attraction to said first magnetic coupling element in order to retain said transverse bar in said closed position; said blind being characterized in that: - said first magnetic coupling element comprises at least one first pair of magnets (25A, 25B), and such first pair comprises a first magnet and a second magnet with opposite polarity with respect to each other; - said second magnetic coupling element comprises at least one second pair of magnets (26A, 26B), and such second pair comprises a third magnet and a fourth magnet with opposite polarity with respect to each other; with said transverse bar in said closed position, said third magnet being coupled in magnetic retention relationship with said first magnet and in magnetic repulsion relationship with said second magnet, and said fourth magnet being coupled in magnetic retention relationship with said second magnet and in magnetic repulsion relationship with said first magnet. - a support frame intended to be fixed to a load-bearing element; - a take-up roller rotatably constrained to said support frame and having a rotation axis; - two lateral guides extended parallel to each other and side-by-side along respective first extension directions substantially orthogonal to the rotation axis of said take-up roller; each said lateral guide extended along the corresponding said first extension direction between a first end, positioned at said take-up roller, and an opposite second end; - a fabric extended between a first edge thereof fixed to said take-up roller and a second edge thereof, and susceptible of sliding between said lateral guides; - a transverse bar fixed to the second edge of said fabric and extended, along a second extension direction parallel to the rotation axis of said take-up roller, between two lateral ends thereof slidably engaged to the corresponding said lateral guides; said transverse bar being movable between an open position, in which said transverse bar is placed at the first ends of said lateral guides, and a closed position, in which said transverse bar is positioned at the second ends of said lateral guides; - at least one first magnetic coupling element, which is fixed to the second end of the corresponding said lateral guide; - at least one second magnetic coupling element, which is fixed to the corresponding lateral end of said transverse bar and, with said transverse bar arranged in said closed position, is engaged via magnetic attraction to said first magnetic coupling element in order to retain said transverse bar in said closed position; - said first magnetic coupling element comprises at least one first pair of magnets (25A, 25B), and such first pair comprises a first magnet and a second magnet with opposite polarity with respect to each other; - said second magnetic coupling element comprises at least one second pair of magnets (26A, 26B), and such second pair comprises a third magnet and a fourth magnet with opposite polarity with respect to each other;