In March 2006, the 30-year-old Rosa was about to leave for work at the county jail when two men tried to rob her.
She pulled out her gun, but before she could fire, the men shot her twice and killed her.
Both men were later caught and convicted.
"She made a difference in everybody she ever met, and that's why we're doing what we're doing here today," said Baca.
Following the ceremony, the memorial sign was installed on the Long Beach Freeway.