A resonant ultrasound technique has been applied to detect cracks in steel spherical rollers. Combining theoretical calculations with RUS measurements, steel rollers provided by a commercial source with various dimensions and aspect ratios were studied. As a result, correlations between aspect ratio and deformation type for some resonant modes were established. Empirical relationships between some specific modes and dimensions were also obtained, with which resonant frequencies of torsional, disk bending, and cylinder bending modes can be predicted from dimensions of the rollers for various aspect ratios. Hence, the testing frequency ranges for a given roller can be determined depending on the type of defects that need to be detected.