From June 2005 to September 2008, Roberto Alvarez held the position of permanent representative of the Dominican Republic to the Organization of American States (OAS) with the rank of ambassador. While at the OAS, he served as chairman of the Permanent Council (2005), chair of the Subcommittee on Partnership for Development Policies of the Permanent Executive Committee of the Inter-American Council for Integral Development (2006–2007), and of the Committee on Juridical and Political Affairs of the Permanent Council (2007–2008). He was a member, with the rank of honorary ambassador, of the Advisory Committee of the Ministry of Foreign Affairs from December 2008 until August 2010, when he resigned. On February 10, 2013, he was elected by the XIX Annual Assembly of Participación Ciudadana to its National Council for two years.

Alvarez received a master's in international relations from the John Hopkins School of Advanced International Studies (SAIS), a master's in comparative law from Georgetown University, and a JD from the Universidad Autónoma de Santo Domingo.