Rosalia finances her adventurous lifestyle as a treasure hunter and deep-sea diver by salvaging valuable artifacts, though she struggles to secure high payments when rightful owners claim them. Her path into the Columbus Egg affair starts when she discovers the amnesiac and injured Fujiko Mine hiding in her home after a traumatic fall. During Fujiko's vulnerability, Rosalia provides shelter and protection, revealing compassion and forming a connection with her. Skilled in combat, particularly knife fighting, Rosalia occasionally falters in confrontations due to distractions. Her personal investment in the Columbus Files originates from her father's research into the Columbus Egg's "Fulgon Energy," fueling her pursuit beyond mere profit. She establishes a temporary, pragmatic alliance with Lupin III and his gang to locate the egg, joining their final assault on its temple stronghold. Rosalia's dynamic with Fujiko weaves protectiveness and lighthearted teasing, exemplified by her joking offer to Lupin about "sharing" Fujiko. Her background centers on her profession and her father's legacy, without documented development or appearances outside this specific special.