The Secretary's business career spanned a vast field which included insurance, banking, real state, shipping, telecommunications,consumer products, retail, pharmaceutical, and food industries, among others.  He was member of the Board of Directors of various firms priorto entering public service and held the position of Philippine Ambassador to the United States in Washington D.C.

As Ambassador Extraordinary and Plenipotentiary to the United States, he was instrumental in securing US$1.2 Billion U.S. funding assistance for the Philippines, bilateral cooperation in counter-terrorism and peace and development in Mindanao, investments in the country's Business Process Outsourcing industry, and greater access for the Philippine exports.  His enduring legacy which continues to benefit the Philippines includes the formation of the Philippine Friendship Caucus Committee of 80 members of the US House of Representatives, retaining the Philippines in the list of approved investment locations in the California Public Employees Retirement System (CalPERS), development of the Reform Program for the Armed Forces of the Philippines, and pioneering the Ambassadors/Consul General Tour of the Philippines, and Bayan Ko-Bahay Ko Program.

In September of 2004, Ambassador del Rosario was conferred the highest possible award, the Order of Sikatuna, Rank of Datu by H.E. President Gloria Macapagal-Arroyo for his oustanding efforts in promoting foreign relations.  He also received the Philippine Army Award from President Aquino for his initiatives as Chairman of the Makati Foundation for Education in 1991.  In early 2001, he received the EDSA II Hereos Award from President Gloria Macapagal-Arroyo in recognition of his efforts in promoting Philippine democracy.  He was recently elevated to the Xavier Hall of Fame in New York City.