Controllable deflection roller

A roller with controllable sag is provided with a revolving hollow roller and a non-rotating crosshead which crosses the hollow roller along its length and on which the hollow roller is supported by a series of support elements actuated by a pressure medium. Separate supply lines (13) lead to the support elements and open out into a connection head (40) at the end (10') of the crosshead, to the connection head (40) are connected the outer connection lines (53). The connection head (40) comprises a double disc rotary slide valve (50) by which the lines (13, 53) can be interrupted and which in the closed state can be separated at a separation surface (47). The individual discs (51, 52) of the double disc rotary slide valve (50) keep both the supply lines (13) and connection lines (53) closed, thus facilitating replacement of the roller as and when required.