  Utilizing the latest and the most sensitive radio and optical catalogs, we
completed a new blazar candidate catalog, Blazar Radio and Optical Survey
(BROS), which includes 88,211 sources located at declination $\delta >
-40^{\circ}$ and outside the galactic plane ($|b| > 10^{\circ}$). We list
compact flat-spectrum radio sources of $\alpha > -0.6$ ($\alpha$ is defined as
$F_{\nu} \propto \nu^\alpha$ ) from 0.15~GHz TGSS and 1.4~GHz NVSS catalogs. We
further identify optical counterparts of the selected sources by cross-matching
with Pan-STARRS1 photometric data. Color-color and color-magnitude plots for
the selected BROS sources clearly show two distinct populations, An
"quasar-like" population consisting of both flat-spectrum radio quasars and BL
Lac type objects. On the other hand, an "elliptical-like" population of mostly
BL Lac-type objects is buried in the elliptical galaxy. We emphasize that the
latter population is missed by previous catalogs but newly emerged in the
present BROS catalog, due to the lower radio flux threshold of our selection.
Model calculations show that the "elliptical-like" population consists of
elliptical galaxies located at redshift z $\lesssim$ 0.5, which is also
supported by the logN-logS distribution of the power-law index of $1.49 \pm
0.05$. This BROS catalog is useful for identifying the electromagnetic
counterparts of ultra-high-energy cosmic rays and PeV neutrinos recently
detected by IceCube, as well as nearby BL Lac objects detectable by future high
sensitivity TeV telescopes, such as Cherenkov Telescope Array.
