  We have undertaken a survey of archived, pointed ROSAT PSPC data for blazars
by correlating the ROSAT WGACAT database with several publicly available radio
catalogs, restricting our candidate list to serendipitous flat radio spectrum
sources (alpha_r <= 0.70). Here we discuss our survey methods, identification
procedure and first results. Our survey is found to be ~ 95% efficient at
finding flat-spectrum radio-loud quasars (FSRQs, 59 of our first 85 IDs) and BL
Lacertae objects (22 of our first 85 IDs), a figure which is comparable to or
greater than that achieved by other radio and X-ray survey techniques.
  The identifications presented here show that all previous samples of blazars
(even when taken together) did not representatively survey the blazar
population, missing critical regions of (L_X,L_R) parameter space within which
large fractions of the blazar population lie. Particularly important is the
identification of a large population of FSRQs (>~ 25% of DXRBS FSRQs) with
ratios of X-ray to radio luminosity >~ 10^-6 (alpha_rx <~ 0.78). In addition,
due to our greater sensitivity, DXRBS has already more than doubled the number
of FSRQs in complete samples with 5 GHz (radio) luminosities between 10^31.5
and 10^33.5 erg/s/Hz and fills in the region of parameter space between X-ray
selected and radio-selected samples of BL Lacs. DXRBS is the very first sample
to contain statistically significant numbers of blazars at low luminosities,
approaching what should be the lower end of the FSRQ luminosity function.
