  We find that pancake dipolar condensates can exhibit a roton-maxon character
of the excitation spectrum, so far only observed in superfluid helium. We also
obtain a condition for the dynamical stability of these condensates. The
spectrum and the border of instability are tunable by varying the particle
density and/or the confining potential. This opens wide possibilities for
manipulating the superfluid properties of dipolar condensates.
