  We present an analysis of the optical spectra available in the Sloan Digital
Sky survey data release nine (SDSS DR9) for the blazars listed in the
ROMA-BZCAT and for the gamma-ray blazar candidates selected according to their
IR colors. First, we adopt a statistical approach based on MonteCarlo
simulations to find the optical counterparts of the blazarslisted in the
ROMA-BZCAT catalog. Then we crossmatched the SDSS spectroscopic catalog with
our selected samples of blazars and gamma-ray blazar candidates searching for
those with optical spectra available to classify our blazar-like sources and,
whenever possible, to confirm their redshifts. Our main objectives are
determining the classification of uncertain blazars listed in the ROMA-BZCAT
and discovering new gamma-ray blazars. For the ROMA-BZCAT sources we
investigated a sample of 84 blazars confirming the classification for 20 of
them and obtaining 18 new redshift estimates. For the gamma-ray blazars,
indicated as potential counterparts of unassociated Fermi sources or with
uncertain nature, we established the blazar-like nature of 8 out the 27 sources
analyzed and confirmed 14 classifications.
