Rosales became a household name when he was paired with actress Angelika dela Cruz in the primetime drama series Esperanza and in the teen horror flick Oka Tokat. His breakout role came when he landed the lead in Pangako Sa 'Yo alongside actress Kristine Hermosa. The success of his team up with Hermosa led to two blockbuster films; Forevermore and Ngayong Nandito Ka.
During February 2014, Rosales became actively involved in a campaign to Free Mali, the lonely elephant who has been living in a small, concrete enclosure at the Manila Zoo for more that 35 years. The campaign is led by animal rights group PETA (People for the Ethical Treatment of Animals) and works toward having Mali transferred to the Boon Lott's Sanctuary in Thailand where she will be given all of the care and natural surroundings that the Manila Zoo cannot provide her with.
Rosales showed his support by posing for a photograph holding up a sign that reads "JERICHO ROSALES WANTS MALI FREED". He stated that "All evidences tell us that Mali is lonely and badly in need of veterinary care ... I don't understand why Mali's transfer has not already happened. She deserves a life that is more than the confines of the Manila Zoo.