  Roman telescope provides the best opportunity to detect a large number of
Isolated Stellar-Mass Black Holes (ISMBHs) through microlensing. Roman will not
only detect long-duration microlensing events caused by ISMBHs, but will also
measure the deflections caused by the ISMBHs, which can be used to estimate
their masses. Recently, Sajadian and Sahu (2023) studied the efficiency of
detecting ISMBHs by Roman through simulation of a large ensemble of such
events. They estimated the resulting errors in the physical parameters of the
lens objects, including their masses, distances, and proper motions through
calculating Fisher and Covariance matrices. Their simulation shows that the
2.3-year time gap between Roman's first three and the last three observing
seasons not only lowers the efficiency of detection, but also makes the
solutions degenerate. We recommend a small amount of additional observations --
about one hour of observations every 10 to 20 days when the Bulge is observable
during the large time gap -- which is equivalent to a total of about one to two
additional days of observations with Roman. This small amount of additional
observations will greatly improve the efficiency and robustness of detection of
ISMBHs, and provide firm estimates of their masses.
