  Stellar surface rotation carries information about stellar
parameters---particularly ages---and thus the large rotational datasets
extracted from Kepler timeseries represent powerful probes of stellar
populations. In this article, we address the challenge of interpreting such
datasets with a forward-modeling exercise. We combine theoretical models of
stellar rotation, a stellar population model for the galaxy, and prescriptions
for observational bias and confusion to predict the rotation distribution in
the Kepler field under standard "vanilla" assumptions. We arrive at two central
conclusions: first, that standard braking models fail to reproduce the observed
distribution at long periods, and second, that the interpretation of the period
distribution is complicated by mixtures of unevolved and evolved stars and
observational uncertainties. By assuming that the amplitude and thus
detectability of rotational signatures is tied to the Rossby number, we show
that the observed period distribution contains an apparent "Rossby edge" at
$\textrm{Ro}_{thresh} = 2.08$, above which long-period, high-Rossby number
stars are either absent or undetected. This $\textrm{Ro}_{thresh}$ is
comparable to the Rossby number at which van Saders et al. (2016) observed the
onset of weakened magnetic braking, and suggests either that this modified
braking is in operation in the full Kepler population, or that stars undergo a
transition in spottedness and activity at a very similar Rossby number. We
discuss the observations necessary to disentangle these competing scenarios.
(abridged)
