Rosa, 45, worked at the facility for years helping hundreds of new firefighters prepare for the job. Family and friends attended Tuesday's naming ceremony.
He was killed when he and other firefighters responded to the 11-story Covenant Manor in the 600 block of East 4th Street in the downtown area.
After extinguishing the blaze, firefighters searched the building and a gunman opened fire.
Rosa died at a hospital.
The 17-year veteran was married with two sons ages 16 and 25.
A 77-year-old suspect identified as Thomas Kim was arrested in the shooting. Kim, a resident of the building, later died in August 2018 from a medical condition at USC Medical Center.