  Current and future optical and near-infrared wide-field surveys have the
potential of finding kilonovae, the optical and infrared counterparts to
neutron star mergers, independently of gravitational-wave or high-energy
gamma-ray burst triggers. The ability to discover fast and faint transients
such as kilonovae largely depends on the area observed, the depth of those
observations, the number of re-visits per field in a given time frame, and the
filters adopted by the survey; it also depends on the ability to perform rapid
follow-up observations to confirm the nature of the transients. In this work,
we assess kilonova detectability in existing simulations of the LSST strategy
for the Vera C. Rubin Wide Fast Deep survey, with focus on comparing rolling to
baseline cadences. Although currently available cadences can enable the
detection of more than 300 kilonovae out to 1400 Mpc over the ten-year survey,
we can expect only 3-32 kilonovae similar to GW170817 to be recognizable as
fast-evolving transients. We also explore the detectability of kilonovae over
the plausible parameter space, focusing on viewing angle and ejecta masses. We
find that observations in redder izy bands are crucial for identification of
nearby (within 300 Mpc) kilonovae that could be spectroscopically classified
more easily than more distant sources. Rubin's potential for serendipitous
kilonova discovery could be increased by gain of efficiency with the employment
of individual 30s exposures (as opposed to 2x15s snap pairs), with the addition
of red-band observations coupled with same-night observations in g- or r-bands,
and possibly with further development of a new rolling-cadence strategy.
