A novel roller conveyor for automated fruits machine vision grader was developed, which can transport quasi-spherical fruits with different size while the fruits rotating with an approximately equal rotational speed, and can present the fruits to cameras for their entire surface inspection. And so, in the interval between two imaging of the image acquisition system, all fruits regardless of size will rotate an approximately equal angle. The generatrix equation of the rollers was deduced, the rules for selecting appropriate design parameters of the conveyor were analyzed, and the selection approach of the conveyor's design parameters was put forward. The image acquisition results showed that apples with diameters of 50~100 millimeters can rotate with an approximately equal rotational speed on the conveyor designed in this work.