  Dipolar Bose-Einstein condensates may present a rotonlike dispersion minimum,
which has yet to be observed in experiments. We discuss a simple method to
reveal roton excitations, based on the response of quasi-two-dimensional
dipolar condensates against a weak lattice potential. By employing numerical
simulations for realistic scenarios, we analyze the response of the system as a
function of both the lattice spacing and the s-wave scattering length, showing
that the roton minimum may be readily revealed in current experiments by the
resonant population of Bragg peaks in time-of-flight measurements.
