How can we approximate sparse graphs and sequences of sparse graphs (with unbounded average degree)? We consider convergence in the first k moments of the graph spectrum (equivalent to the numbers of closed k-walks) appropriately normalized. We introduce a simple random graph model that captures the limiting spectra of many sequences of interest, including the sequence of hypercube graphs. The random overlapping communities (ROC) model is specified by a distribution on pairs (s, q), s ∈ Z + , q ∈ (0, 1]. A graph on n vertices with average degree 𝑑 is generated by repeatedly picking pairs (s, q) from the distribution, adding an Erdős-Rényi random graph of edge density q on a subset of vertices chosen by including each vertex with probability s∕n, and repeating this process so that the expected degree is 𝑑. We also show that ROC graphs exhibit an inverse relationship between degree and clustering coefficient, a characteristic of many real-world networks.