A waste catchment system for rollers (2), in particular printing press rollers, comprises an elongate tray (4), a blade assembly (6) attached to the tray (4) and including a blade (10) the free edge of which engages the roller (2) to remove waste material from the roller (2) and direct it towards the tray (4), and a liner (12) within the tray (4) to receive therein the waste material, the blade assembly (6) and one edge of the liner (12) being provided with co-operating male/female elements (20, 22) which are a friction push-fit one into the other to effect a releasable sealing connection between the blade assembly (6) and the liner (12).