  In this paper, the availability of multi-wavelength optical/infrared
information of FIRST (Faint Images of the Radio Sky at 20 cm) radio sources
counterparts over ~9.2 deg^{2} in Bootes field and ~2.4 deg^{2} in Cetus field
is exploited to infer the physical properties of the faint radio population.
The radio sources optically identified have been divided into resolved galaxies
and stellar-like objects finding that the faint radio population is mainly
composed of early-type galaxies with very red colour (Bw-R~4.6). A total number
of 57 counterparts of FIRST radio sources have extremely red colour (R-K>5).
Photometric redshift from Hyperz implies that the Extremely Red Objects (EROs)
counterparts to FIRST radio sources are mostly located in the range z=0.7-2,
with the bulk of the population at z\sim 1. Taking advantage of the near
infrared imaging with FLAMEX (FLAMINGOS Extragalactic Infrared Survey), the
EROs counterparts to FIRST radio sources are separated into passively-evolving
and dusty star-forming galaxies using their RJK colours; the relatively blue
J-K of these galaxies suggest that most are old elliptical galaxies (18/25)
rather than dusty starburst (7/25). A total of 15 Distant Red Galaxy (DRGs)
have been identified as counterparts to FIRST radio sources in Cetus field and
3 DRGs in Bo\"{o}tes field with J-K>2.3.
