  Many open questions in X-ray astronomy are limited by the relatively small
number of objects in uniform optically-identified samples, especially when rare
subclasses are considered, or subsets isolated to search for evolution or
correlations between wavebands. We describe initial results of a program aimed
to ultimately yield 10^4 X-ray source identifications--a sample about an order
of magnitude larger than earlier efforts. The technique employs X-ray data from
the ROSAT All-Sky Survey (RASS), and optical imaging and spectroscopic followup
from the Sloan Digital Sky Survey (SDSS). Optical objects in the SDSS catalogs
are automatically cross-correlated with RASS X-ray source positions; then
priorities for follow-on SDSS optical spectra of candidate counterparts are
automatically assigned using an algorithm based on the known fx/fopt ratios for
various classes of X-ray emitters. SDSS parameters for optical morphology,
magnitude, colors, plus FIRST radio data, serve as proxies for object class.
  Initial application of this approach to 1400 deg^2 of sky provides a catalog
of 1200 spectroscopically confirmed quasars/AGN that are probable RASS
identifications. Most of the IDs are new, and only a few percent of the AGN are
likely to be random superpositions. The magnitude and redshift ranges of the
counterparts extend over 15<m<21 and 0.03<z<3.6. Although most IDs are quasars
and Sy 1s, a variety of other AGN subclasses are also sampled. Substantial
numbers of rare AGN are found, including more than 130 narrow-line Seyfert 1s
and 45 BL Lac candidates. These results already provide a sizeable set of new
IDs, show utility of the sample in multi-waveband studies, and demonstrate the
capability of the RASS/SDSS approach to efficiently proceed towards the largest
homogeneously selected/observed sample of X-ray emitting AGN. Abridged Abstract
