A rotorcraft ducted rotor comprising a rotary assembly arranged in a passage to rotate about an axis of symmetry (AX1). The rotary assembly (15) has a plurality of blades (20), each fastened to a hub (16), each blade (20) complies with a twisting relationship defining an angle of twist lying in the range zero degrees inclusive to 5 degrees inclusive. Spanwise, each blade (20) comprises a first zone (21) followed by a second zone (22), which second zone presents rearward sweep, being provided with a second trailing edge (30″) situated downstream from a first trailing edge (30′) of the first zone (21). Each first zone (21) includes a root (24) connected to the hub (16) by a fastener device (40) having a rolling bearing (45) without clearance and a conical laminated abutment (50).