The invention relates to a system having: a first longitudinal member and a second longitudinal member arranged symmetrical to the first longitudinal member in relation to a longitudinal mid-plane of the conveyor system, to define a forward movement track and a return track of the rollers (4); a connecting crossbeam (6) for connecting the longitudinal members. The longitudinal members have: an upper surface defining the forward movement track (2) on which the rollers (4) roll; a lower surface defining the return track (3) on which the rollers (4) roll; an inner surface provided with means for fixing the longitudinal members; an outer surface. The first longitudinal member is connected to the second longitudinal member by means of a connecting crossbeam (6) to ensure a necessary tolerance between longitudinal members.