  Population III (Pop III) stars formed out of metal free gas in minihalos at
$z>20$. While their ignition ended the Dark Ages and begin enrichment of the
IGM, their mass distribution remains unconstrained. To date, no confirmed Pop
III star has been observed and their direct detection is beyond the reach of
the James Webb Space Telescope (JWST) without gravitational lensing. However, a
subset of massive Pop III stars end their lives in pair instability supernova
(PISN). With typical energies of $\sim10^{53}$~erg, PISN light curve peaks are
bright enough to be detectable by JWST and the Roman Space Telescope. The
fundamental question of this work is whether or not observed PISN can be used
as a diagnostic of the Pop III IMF. In this work, we use a model of the
formation of the first stars to determine the dependence of PISN rates at
$z~>~5$ for a range of Pop III power law IMFs ($\alpha~=~0.2~-~2.35$) and,
critically, the method by which the IMF is populated. At $z~>~15$, we predict
typical rates of $10^{-2}~-~10^2$ per deg$^{2}$ per year which will produce
$10^{-3}~-~0.1$/year in a single NIRCam pointing and $0.003~-~30$/year in a
single Roman pointing with $0.1~-~1000$ per year detected in the HLTDS. Our
work highlights that theoretical modeling of PISN rates is required if upcoming
PISN studies with JWST and Roman are going to constrain the Pop III IMF.
