We propose a new method for identifying the role of a vertex in a social network. Existing well-known metrics of node centrality such as betweenness, degree and closeness do not take the community structure within a network into consideration. Furthermore, existing proposed community-based roles are defined using cliques, and thereby it is difficult to discover vertices with only few links that bridge communities. To overcome the shortcomings, we propose three community-oriented roles, bridges, gateways and hubs, without knowledge on the community structure, for representing vertices that bridge communities. We believe that detecting the roles in a social network is useful because such nodes are valuable by themselves due to their intermediate roles between communities and also because the nodes are likely to provide a deeper understanding of the communities. Our method outperforms the state-of-the-art method through experiments using data of DBLP records in terms of the subjective validness of the outputs.