A roller assembly facilitates travel of a watercraft hull on a floating dock having a longitudinal, keel-receiving valley with a pair of flanking ridges supporting opposite sides of the hull during docking and launching of the craft. Pockets in the ridges contain wheels mounted on circumferential planes parallel to the ridges for rotation on axles seated in the pockets. The upper portions of the wheels protrude above the crests of the ridges and the axle end bearing portions cooperate with the seats in the pockets to list the circumferential planes toward the valley and approximately perpendicular to the hull sides. For optimal performance, two or more roller assemblies can be arranged in-line and spaced apart longitudinally in each of the ridges. A brake stops the docking motion of the watercraft onto the dock. Multiple docks can be serially connected without use of special tools or underwater assembly steps.