  We present and analyze the optical and X-ray catalogs of moderate-redshift
cluster candidates from the ROSAT Optical X-ray Survey, or ROXS. The survey
covers 4.8 square degrees (23 ROSAT PSPC pointings). The cross-correlated
cluster catalogs were constructed by comparing two independent catalogs
extracted from the optical and X-ray bandpasses, using a matched filter
technique for the optical data and a wavelet technique for the X-ray data. We
cross-id cluster candidates in each catalog. In Paper II we present the cluster
catalogs and a numerical simulation of ROXS. We also present color-magnitude
plots for several cluster candidates, and examine the prominence of the red
sequence in each. We find that the X-ray clusters analyzed in this way do not
all have a prominent red sequence. We conclude that while the red sequence may
be distinct for massive, virialized clusters, it may be less so for lower-mass
clusters at even moderate redshifts. Multiple, complementary methods of
selecting and defining clusters may be essential, particularly at high redshift
where all methods run into completeness limits, incomplete understanding of
physical evolution, and projection effects.
