We use spectroscopic observations of the gravitationally lensed systems SDSS0924+0219(BC), Q1355-2257(AB), and SDSS1029+2623(BC) to analyze microlensing and dust extinction in the observed components. We detect chromatic microlensing effects in the continuum and microlensing in the broad emission line profiles of the systems SDSS0924+0219(BC) and Q1355-2257(AB). Using magnification maps to simulate microlensing and modeling the emitting region as a Gaussian intensity profile with size r(s) proportional to lambda(p), we obtain the probability density functions for a logarithmic size prior to lambda(rest-frame) = 3533 angstrom. In the case of SDSS0924+0219, we obtain r(s) = 4(2)(+3) root M/M-circle dot lt-d (at 1 sigma), which is larger than the range of other estimates, and p = 0.8 +/- 0.2 (at 1 sigma), which is smaller than predicted by the thin disk theory, but still in agreement with previous results. In the case of Q1355-2257 we obtain (at 1 sigma) r(s) = 3.6(-1.6)(+3.0) root M/M-circle dot lt-d, which is also larger than the theoretical prediction, and p = 2.0 +/- 0.7, which is in agreement with the theory within errors. SDSS1029+2326 spectra show evidence of extinction, probably produced by a galaxy in the vicinity of image C. Fitting an extinction curve to the data we estimate Delta E similar to 0.2 in agreement with previous results. We found no evidence of microlensing for this system.