A multifunction rotary tool for milling and roughening backs of blocks of pages to be bound by a bookbinding machine comprises a cylindrical base defining a rotation axis, a first annular member adapted to be secured to the cylindrical base and having an outer edge, a crown of milling blades formed in the first annular member proximate to its outer edge and defining a cutting plane perpendicular to the rotation axis, and a plurality of roughening inserts securable to the cylindrical base along a circular area radially offset from the crown of milling blades. Each insert comprises a cylindrical body with a hook-shaped end portion defined by an upper edge with a sharp tip designed to penetrate the block back in a perpendicular cut. The end portion comprises a recessed surface adapted to tear and push downwards the cut material without removing it.