Roving frame of a spinning line, comprising: - a drawing device comprising at least two pairs of pressure-coupled rollers, suitable for drawing a web and making a roving; - first means of moving to move the rollers of the drawing device; - a winding device, downstream of the drawing device for winding the roving in spools; - second means of moving for the winding device; - an intermediate region positioned downstream of the drawing device and upstream of the winding device, traversed by the roving during normal machining; - a system for detecting breakages of the roving comprising: a) a detection devices associable in a detachable manner to the frame of the roving frame comprising a plurality of sensors, positioned in the intermediate region; b) a processing device associated with each sensor, suitable for picking up the primitive signal (Sp) and for emitting a processed signal, able to act on the primitive signal (Sp) according to a low pass filter or a timer; - a control device, operatively connected to the processing devices to pick up the processed signals, and to the first and second moving means, to send command signals to these and stop the drawing device and the winding device in the presence of a processed signal indicating a breakage of the roving; characterised in that each detection device is situated between two rovings, and comprises: - a pair of sensors, each associated with a roving and each suitable for detecting the presence of the roving in a relative detection zone of the intermediate region and for emitting a relative primitive signal (Sp); - a casing in which said sensors are housed, having longitudinally opposite apertures from which said sensors look out, and wherein the sensors are positioned in the casing, or the casing is fitted to the frame, so that the direction of emission of the rays emitted by a sensor are misaligned with those of an adjacent sensor, so as to prevent interferences. - a drawing device comprising at least two pairs of pressure-coupled rollers, suitable for drawing a web and making a roving; - first means of moving to move the rollers of the drawing device; - a winding device, downstream of the drawing device for winding the roving in spools; - second means of moving for the winding device; - an intermediate region positioned downstream of the drawing device and upstream of the winding device, traversed by the roving during normal machining; - a system for detecting breakages of the roving comprising: a) a detection devices associable in a detachable manner to the frame of the roving frame comprising a plurality of sensors, positioned in the intermediate region; b) a processing device associated with each sensor, suitable for picking up the primitive signal (Sp) and for emitting a processed signal, able to act on the primitive signal (Sp) according to a low pass filter or a timer; a) a detection devices associable in a detachable manner to the frame of the roving frame comprising a plurality of sensors, positioned in the intermediate region; b) a processing device associated with each sensor, suitable for picking up the primitive signal (Sp) and for emitting a processed signal, able to act on the primitive signal (Sp) according to a low pass filter or a timer; - a control device, operatively connected to the processing devices to pick up the processed signals, and to the first and second moving means, to send command signals to these and stop the drawing device and the winding device in the presence of a processed signal indicating a breakage of the roving; characterised in that each detection device is situated between two rovings, and comprises: - a pair of sensors, each associated with a roving and each suitable for detecting the presence of the roving in a relative detection zone of the intermediate region and for emitting a relative primitive signal (Sp); - a casing in which said sensors are housed, having longitudinally opposite apertures from which said sensors look out, and wherein the sensors are positioned in the casing, or the casing is fitted to the frame, so that the direction of emission of the rays emitted by a sensor are misaligned with those of an adjacent sensor, so as to prevent interferences.