His life has not yet been thoroughly studied. The earliest information available shows that he may have lived and worked on Chios, an island in the Aegean, in the service of the GenoeseGiustiniani family; the connection can be made from the dedication to one of his 1560 books of madrigals. In 1560 he assisted at the wedding of Emmanuel Philibert of Savoy and Marguerite of Valois, which took place in Nice. In 1566 at the latest he went to Florence, where he served Ferdinando I de' Medici as a composer, alongside Alessandro Striggio, and Francesco Corteccia, whose career by then had begun to wane. By 1579 he was in the employ of either Albrecht V, or William V. The intermedio performed in Florence in 1583 alongside Fedini's play Le due Persile may have been his work. Connections between the Medici and Bavarian courts were close through the period, and composers often passed between them. Nothing certain is yet known of Rossetto's career after 1580.
Music
All of his surviving music is vocal, and includes madrigals and motets, some of which were probably intended for performance as intermedii, musical interludes between acts of plays. Along with the other Medici composers, taking part in a trend of the time, he wrote gigantic polychoral compositions. One of the largest polychoral works ever composed, at least prior to modern times, was his huge 50-voice motetConsolamini popule meus. The date of the composition is unknown, but the manuscript is at the Bayerische Staatsbibliothek in Munich, suggesting he wrote it while in the service of the Bavarian court. Only a handful of larger compositions are known: Alessandro Striggio's colossal 40 and 60 voice Missa sopra Ecco sì beato giorno, and the 17th century 53-voice Missa Salisburgensis attributed to Heinrich Ignaz Biber. Rossetto also composed three books of madrigals, for four, five, and six voices, respectively, and an ambitious setting of the Lamento d'Olimpia, in seventeen parts, for from four to ten voices, which he published in Venice in 1567. In addition to his secular music, he published a book of motets in Nuremberg in 1573, Novae quaedam sacrae cantiones, quas vulgo motetas vocant, for five and six voices. In his madrigals he uses chromaticism creatively, and he liked to write both madrigals and motets in groups, as did the other Medici composers. Much of his music is intended to be accompanied by instruments, another characteristic of Florentine polyphony of the period.
