  Constant-roll inflation was recently introduced by Motohashi, Starobinsky and
Yokoyama as a phenomenological way to parametrize deviations from the slow-roll
scenarios. In this paper, we investigate the dynamics of both the background
and the perturbations in this model, without making any slow-roll assumptions.
The perturbation spectra are computed with an efficient and accurate novel
method that allowed us to quickly scan the parameter space of constant-roll
inflation. We derive the constraints on the model parameters from the cosmic
microwave background anisotropy measurements provided by the joint analysis of
the Planck Collaboration and the BICEP2/Keck Array data.
