The conditioning rolls of a crop harvester have intermeshing metal ribs arranged in a herringbone pattern, each rib comprising a pair of end-to-end segments that converge spirally from opposite ends of the roll to a centermost apex. Alternative embodiments provide a single pair of metal herringbone rolls, two pairs of metal herringbone rolls, or a front pair of metal herringbone rolls and a rear pair of compressible surface herringbone rolls.