The invention relates to a roller shutter box comprising an upper profile 10 and a lower profile 20, detachably connected to the upper profile by means of an extremal coupling portion 21 which engages a housing seat 11 made at an extremal portion 10' of the upper profile, the latter portion having a substantially Z-shaped cross- section. The housing seat 11 is delimited in particular by an angled end portion 15 which defines with the main body 12 of the upper profile the access opening 16 to the seat. The coupling portion comprises a tongue 23 which engages the housing seat in catching relation. The angled end portion defines a flat surface 18 facing the seat and forms an acute angle a in relation to the perpendicular to a plane tl which is tangent to the main body 12. The coupling portion has two humps 24, 25 of opposed concavity and sized so that one hump touches the angled end portion, while the other touches the main body.