  We examine the quenching characteristics of $328$ isolated dwarf galaxies
$\left(10^{8} < M_{\rm star}/M_\odot < 10^{10} \right)$ within the \Rom{}
cosmological hydrodynamic simulation. Using mock observation methods, we
identify isolated dwarf galaxies with quenched star formation and make direct
comparisons to the quenched fraction in the NASA Sloan Atlas (NSA). Similar to
other cosmological simulations, we find a population of quenched, isolated
dwarf galaxies below $M_{\rm star} < 10^{9} M_\odot$ not detected within the
NSA. We find that the presence of massive black holes (MBHs) in \Rom{} is
largely responsible for the quenched, isolated dwarfs, while isolated dwarfs
without an MBH are consistent with quiescent fractions observed in the field.
Quenching occurs between $z=0.5-1$, during which the available supply of
star-forming gas is heated or evacuated by MBH feedback. Mergers or
interactions seem to play little to no role in triggering the MBH feedback. At
low stellar masses, $M_{\rm star} \lesssim 10^{9.3} M_\odot$, quenching
proceeds across several Gyr as the MBH slowly heats up gas in the central
regions. At higher stellar masses, $M_{\rm star} \gtrsim 10^{9.3} M_\odot$,
quenching occurs rapidly within $1$ Gyr, with the MBH evacuating gas from the
central few kpc of the galaxy and driving it to the outskirts of the halo. Our
results indicate the possibility of substantial star formation suppression via
MBH feedback within dwarf galaxies in the field. On the other hand, the
apparent over-quenching of dwarf galaxies due to MBH suggests higher resolution
and/or better modeling is required for MBHs in dwarfs, and quenched fractions
offer the opportunity to constrain current models.
