  [Abridged] The Nancy Grace Roman Space Telescope will be one of several
flagship survey facilities operating over the next decade starting $\sim$2025.
The deep near-IR imaging that Roman will deliver will be highly complementary
to the capabilities of other survey telescopes that will operate
contemporaneously, particularly those that can provide data at different
wavelengths and messengers, or different time intervals. Combining data from
multiple facilities can provide important astrophysical insights, provided the
data acquisition is carefully scheduled, and careful plans are made for
appropriate joint data analyses. In this White Paper, we discuss the broad
range of science that would be enabled by coordinating Roman observations of
the Galactic Bulge with those of the Vera C. Rubin Observatory. Specifically,
we discuss how Roman's characterization of lensing events caused by exoplanets,
stellar systems and stellar remnants can be enhanced by data from Rubin. The
same data will also be highly advantageous for the determination of stellar
properties, and for distinguishing exoplanetary transits. It will enable more
accurate period-color-luminosity relationships to be measured for RR~Lyrae
throughout the Milky Way Bulge and Bar, probing galactic structure and
dynamics. But we stress that this is only a sample of the full potential and
advocate for a more complete study to be made as a joint effort between these
major projects. We note that we do not suggest any changes beyond the
established Science Requirements for the RGBTDS, in terms of survey footprint
or filter selection.
