We present experimental and numerical studies of nonlinear magneto-optical rotation (NMOR) in rubidium vapor excited with resonant light tuned to the 5 2 S 1/2 → 6 2 P 1/2 absorption line (421 nm). Contrary to the experiments performed to date on the strong D1 or D2 lines, in this case, the spontaneous decay of the excited state 6 (2009), we demonstrate that despite the complexity of the structure, NMOR can be adequately described with a model, where only a single excited-state relaxation rate is used.