Marcello Rosa was born on June 16, 1935, in Abbazia, a town on the Kvarner coast that belonged to the Kingdom of Italy at the time of his birth; the area was ceded to Yugoslavia after the Second World War and is today Opatija, Croatia. His family moved to Rome in the postwar years, where Rosa grew up, studied classical piano with his mother, and, after the war, turned to the trombone and to jazz history. He made his public debut in 1954 and spent the rest of his life based in Rome.

By the mid-1950s Rosa was a founding-era member of the Roman New Orleans Jazz Band, the New Orleans-revival combo that anchored Rome's traditional jazz scene, and he later spent seven years in a related lineup billed as the Seconda Roman. In 1967 he recorded Noi Maggiorenni (RCA Italiana) as part of the Quartetto Di Carlo Loffredo, alongside bassist Carlo Loffredo, trumpeter Piero Saraceni and tuba player Carlo Sili, a Discogs-confirmed session tagged Dixieland. He formed his own Swinging' Dance Band toward the end of the 1960s and issued New! Dixieland Sound (Contape, 1969) under his own name.

Alongside performing, Rosa built a parallel career in Italian broadcasting. He won a national RAI competition for radio programmers in 1963 - the same competition that also brought in Gianni Boncompagni and Renzo Arbore - and in 1968 created and hosted Jazz Jockey, Italy's first dedicated jazz radio program. He later hosted the jazz program Un Certo Ritmo and worked for years as an author of RAI jazz broadcasts, becoming one of the country's principal on-air advocates for the music alongside his own playing.

In 1973 Rosa led Jazz A Confronto 2 (Horo Records), an unusual session built around a small choir of trombones: Rosa, Dino Piana, Alberto Collatina and Aldo Josue on trombones, with Giancarlo Schiaffini on tuba, Enrico Pieranunzi on piano and Bruno Tommaso on contrabass, part of Horo's landmark "Jazz A Confronto" series documenting Italian jazz musicians of the era. He returned to leader recordings through the 1980s and 1990s: a self-titled 1985 quartet session on Soundstudio with tenor saxophonist Enzo Scoppa, The Blue Rose (1990), Jass & Jazz (1990, with trumpeter Flavio Boltro and bassist Massimo Moriconi), and La voce del Trombone (1993, V.A.I.). An undated Penta Flowers release, & Guests, billed to the Enzo Scoppa Quartet, carries Rosa alongside guitarist Eddy Palermo, trumpeter Cicci Santucci, Moriconi and drummer Giampaolo Ascolese.

Institutional recognition ran alongside the recording career: RAI Radiouno's "30 Years of Jazz" award in 1984, the Ente dello Spettacolo's "Colonna Sonora '87" prize, membership in the Grande Orchestra Nazionale di Jazz from 1992, the presidency of the Associazione Nazionale Musicisti Jazz in 1993, and the European Tourism Center's "European Personality" prize in 1997. Italian press biographies also describe Rosa performing at international festivals and clubs alongside visiting American jazz figures over the decades, among them Duke Ellington, Lionel Hampton, Slide Hampton, Earl Hines, Albert Nicholas, Trummy Young, Peanuts Hucko, Bill Coleman, Milt Jackson, Kay Winding and Tony Scott, and representing Italy at the Comblain-La-Tour International Jazz Festival in Belgium across four consecutive years in the 1960s, including 1965, when Italian sources describe him as the festival's sole Italian representative. These are reported consistently across independent Italian sources as live performance and festival history, but no shared studio recording credit for any of these names was found on Discogs, so none is treated here as a documented collaboration.

Rosa's fullest studio credit as a leader is A Child Is Born (2007), a session that brought together Enrico Pieranunzi and Giorgio Cuscito on piano, Giancarlo Schiaffini alongside Rosa on trombone, trumpeter Fabrizio Bosso, and saxophonists Enzo Scoppa and Max Ionata, with Rosa himself also credited on piano and trumpet. In 2014 he published a memoir, Amari Accordi, and in 2020, for his 85th birthday, he released The World on a Slide (AlfaMusic), a 16-track album built entirely around the trombone and featuring 18 European trombonists; the record is documented in press coverage and on video but has no Discogs entry. Marcello Rosa died in Rome on December 19, 2024, at 89. Rome's Casa del Jazz and the Fondazione Musica per Roma both issued tributes on his death, and Italian obituaries described him as a pioneering figure of jazz in Italy.

Rosa's musical identity was formed in New Orleans-revival Dixieland, the idiom of the Roman New Orleans Jazz Band and his own early leader records, and he stayed rooted in that trombone-forward, small-combo tradition across six decades of recording. His catalog also shows real range within that base: the trombone-choir concept of Jazz A Confronto 2 pushed his own instrument to the center of a more exploratory ensemble piece, and A Child Is Born placed him alongside a younger generation of Italian post-bop and hard-bop players. Running underneath the playing career was a second, less common identity for an Italian jazz musician of his generation: a working broadcaster who used Italian state radio to build an audience for the music he played, from his 1968 program Jazz Jockey onward.