In this paper, we propose a new framework for the construction of the likelihood of discretely observed differential equations driven by rough paths. The paper is split in two parts: in the first part, we construct the exact likelihood for a discretely observed rough differential equation, driven by a piecewise linear path. In the second part, we use this likelihood to construct approximate likelihoods for discretely observed differential equations driven by a general class of rough paths. Finally, we study the behaviour of the approximate likelihoods when the sampling frequency tends to infinity.