The consistency of roller diameter, namely the diameters deviation of rollers, is one of the most important machining errors. However, the influence of roller diameter consistency on bearing performance has not received enough attention compared with other machining errors. By modifying the elastic deformation between roller and raceways, this study presents a quasi-dynamic model for roller bearings considering the consistency of roller diameter. Based on the presented model, the influences of the roller diameter consistency on the bearing vibration and contact load fluctuations between rollers and raceways have been analyzed. The results show that the consistency of roller diameter significantly affects the amplitude and the characteristic values of the vibration acceleration of roller bearings. In addition, the roller diameter deviation leads to a significant increase in the maximum values and the fluctuations range of contact load between rollers and raceways, which is a potential factor in causing the actual fatigue life of the bearings is significantly lower than the predicted value. The results will provide a theoretical basis for the development of machining error standards for high-performance roller bearings.