A mine roof support assembly comprises a pair of adjacent mine roof support units and apparatus for guiding and aligning these units. Each of the units has a floor sill and telescopic props for bracing against the roof of a mine excavation. Shifting ram means are provided for displacing the units in the direction in which the working face advances. The guiding and aligning apparatus comprises two telescopic guide rods which are pivotally connected to the units. Each guide rod is constituted by a springless, non-hydraulic piston-and-cylinder device. The two guide rods are inclined at an acute angle to one another in such a way that, when the units are positioned side-by-side, one of the guide rods is completely retracted and its axis is perpendicular to the direction in which the units are displaced, and, when one of the units has been displaced by the shifting ram means relative to the other unit, the other guide rod is completely retracted.