We present a simple mathematical framework for the description of the dynamics of glassy systems in terms of a random walk in a complex energy landscape pictured as a network of minima. We show how to use the tools developed for the study of dynamical processes on complex networks, in order to go beyond mean-field models that consider that all minima are connected to each other. We consider several possibilities for the rates of transitions between minima, and show that in all cases the existence of a glassy phase depends on a delicate interplay between the network's topology and the relationship between the energy and degree of a minimum. Interestingly, the network's degree correlations and the details of the transition rates do not play any role in the existence (or in the value) of the transition temperature, but have an impact only on more involved properties. For Glauber or Metropolis rates in particular, we find that the low temperature phase can be further divided into two regions with different scaling properties of the average trapping time. Overall, our results rationalize and link the empirical findings concerning correlations between the energies of the minima and their degrees, and should stimulate further investigations on this issue.