1. Roll paper feed device (1) for a printing machine (2), comprising a cradle (3) provided with side cheeks (4), means (5, 7) at the bottom of the cradle for supporting a freely rotating paper roll (6) whenever the free end of the paper web (10) is subjected to a traction (9), braking means (13) for the rotating roll (6), which are joined to the cradle and have at least one elastic bearing member (14) against a side of the roll, which member comprises at least one elastically deformable arm (19) joined to the cradle and a protruding zone (16) situated at the free end of the arm and engaged through an opening (17) in the cheek and protruding relative to the inner face of the latter; the protruding zone is in the form of a protruding stub having a flat bearing surface (18) peripherally surrounded by an inclined surface (24, 25) suitable for sliding over the sides of the roll when this is introduced in the cradle.