  Reflected starlight measurements will open a new path in the characterization
of directly imaged exoplanets. However, we still lack a population study of
known targets amenable to this technique. Here, we investigate which of the
about 4300 exoplanets confirmed to date are accessible to the Roman Space
Telescope's coronagraph (CGI) in reflected starlight at reference wavelengths
$\lambda$=575, 730 and 825 nm. We carry out a population study and also address
the prospects for phase-curve measurements. We used the NASA Exoplanet Archive
as a reference for planet and star properties, and explored the impact of their
uncertainties on the exoplanet's detectability by applying statistical
arguments. We define a planet as Roman-accessible on the basis of the
instrument inner and outer working angles and its minimum planet-to-star
constrast (IWA, OWA, $C_{min}$). We adopt for these technical specifications
three plausible configurations labeled as pessimistic, intermediate and
optimistic. Our key outputs for each exoplanet are its probability of being
Roman-accessible ($P_{access}$), the range of observable phase angles, the
evolution of its equilibrium temperature, the number of days per orbit that it
is accessible and its transit probability. In the optimistic scenario, we find
26 Roman-accessible exoplanets with $P_{access}$>25% and host stars brighter
than $V$=7 mag. This population is biased towards planets more massive than
Jupiter but also includes the super-Earths tau Cet e and f which orbit near
their star's habitable zone. A total of 13 planets are part of multiplanet
systems, 3 of them with known transiting companions, offering opportunities for
contemporaneous characterization. The intermediate and pessimistic scenarios
yield 10 and 3 Roman-accessible exoplanets, respectively. We find that
inclination estimates (e.g. with astrometry) are key for refining the
detectability prospects.
