The roof of an underground mine working which is newly exposed by a mining machine passing along a face of the working is supported by applying a flexible mat to the roof and underpinning the mat by self-advancing roof supports. A supply of mat is stored in a region which is already supported by the roof supports, is fed from the store in a first direction, and turned through a right-angle to extend along the newly exposed face. The device which turns the mat and applies it to the roof may have its vertical position controlled in accordance with the vertical position of a cutting cylinder of the mining machine.