  Graphene mechanical resonators have recently attracted considerable attention
for use in precision force and mass sensing applications. To date, readout of
their oscillatory motion has typically required cryogenic conditions to achieve
high sensitivity, restricting their range of applications. Here we report the
first demonstration of evanescent optical readout of graphene motion, using a
scheme which does not require cryogenic conditions and exhibits enhanced
sensitivity and bandwidth at room temperature. We utilise a high $Q$
microsphere to enable evanescent readout of a 70 $\mu$m diameter graphene drum
resonator with a signal-to-noise ratio of greater than 25 dB, corresponding to
a transduction sensitivity of $S_{N}^{1/2} = $ 2.6 $\times 10^{-13}$ m
$\mathrm{Hz}^{-1/2}$. The sensitivity of force measurements using this
resonator is limited by the thermal noise driving the resonator, corresponding
to a force sensitivity of $F_{min} = 1.5 \times 10^{-16}$ N
${\mathrm{Hz}}^{-1/2}$ with a bandwidth of 35 kHz at room temperature (T = 300
K). Measurements on a 30 $\mu$m graphene drum had sufficient sensitivity to
resolve the lowest three thermally driven mechanical resonances.
