As one kind of anamorphic laser triangulation displacement sensor, rotationally symmetric triangulation (RST) has a lot of advantages comparing to traditional ones. Laser speckle and CCD noise are also two fundamental uncertainty factors in this kind of sensors. The analytic expression of centroid uncertainty limit from speckle in RST sensor is derived in this paper. It is shown that the uncertainty limit in RST, and also in anamorphic triangulation, is dependent on the solid angle subtended by entrance pupil as seen from the illuminated laser spot, as well as the laser wavelength. Because it's very easy to get a bigger entrance pupil in RST than in traditional laser triangulation, the centroid uncertainty limit from speckle in RST is much smaller. The CCD noise in RST and anamorphic laser triangulation is dependent on photon shot noise, dark current, photo-response non-uniformity, and cross talk. The centroid uncertainty limit from CCD noise in this case is described by 1-D Cramer-Rao lower bound, and is also smaller than in traditional triangulation. By using more CCD pixels, RST is less sensitive to noise level. Results of simulation and experiments verify the result of deriving.