Abstract: A roller for rewinding and tensioning a flexible element, the element having a greater length than width, includes a tubular body to which one end of the flexible element is fixed; a shaft positioned so that it is coaxial to the tubular body, the two being attached in such a way that they may rotate relative to one another about a shared axis; at least one helical spring driving element made of wire, housed in the tubular body, the ends of the spring being connected, by means of support and connecting parts, to the shaft and the tubular body so as to contrast the reciprocal rotation in the direction of unwinding of the flexible element, at least one of the support and connecting parts being able to slide along the axis of the roller on relative guides so as to position itself along the shaft, adapting each time to the variations in the axial length of the spring driving element, the variations being caused by the unwinding and rewinding of the flexible element on the roller.