A compressor roll assembly (41) for a forage harvester comprises a set of closely adjacent, cooperating compressor rolls (44), operable to crack maize kernels in the crop material with their a substantially cylindric crop-engaging surfaces (45), which are composed by a plurality of exchangeable surface elements (60,63). The rolls (44) are installed within a frame (42) and their shafts (73, 74) are journalled in bearing housings (78-81) which lie outside said frame (42). The mounting of these housings (78-81) permits the removal of a complete roll (44), whereafter direct access is given to the bolt means (70) for replacement of any of the elements (60, 63), without any need for prior disassembly of the bearing housings (78-81) from the compressor roll (44).