Initially, Roberto was educated at Brera Academy in Milan. In 1942, he started to attend the Polytechnic University of Milan. Some time later, in 1946, Sambonet enrolled at the Accademia Carrara di Belle Arti di Bergamo.
During the period from 1946 to 1949, Roberto exhibited his paintings in Milan, Stockholm and Venice. In 1947, he traveled to Paris. Upon his return to Italy, Sambonet exhibited his works together with artists of Pittura group.
In 1949, the painter left for Brazil. In São Paulo, Roberto met the architect Lina Bo Bardi, who later organized Sambonet's personal exhibition at São Paulo Museum of Art and the Museum of Modern Art in Rio de Janeiro.
In 1951, he obtained permission from psychiatrist Edu Machado Gomes to make a series of drawings at Juqueri Psychiatric Hospital, located in Franco da Rocha, São Paulo. The set of drawings forms the series entitled Madness.
Between 1951 and 1953, Roberto held the post of a professor of drawing and painting at the Institute of Contemporary Art (IAC) at Masp.
In 1952, the painter produced drawings and the poster for the first Brazilian fashion show. The following year, he returned to Italy, opened a studio in Milan and decided to devote himself mainly to design and painting.
From 1957 to 1960, Roberto served as an art director of the Zodiac magazine. In 1974, together with Bruno Munari, Bob Noorda and Pino Tovaglia, Roberto designed the Lombardy Region brand.
As a designer, he collaborated with some companies, such as Baccarat (crystals), Archimede Seguso (Murano glassware), Tiffany (jewels) and Richard Ginori (porcelain). While working as a designer, Sambonet didn't stop painting.
Roberto Sambonet was the president of the Italian department of Alliance Graphique Internationale.
Roberto was married to Luisa Bernacchi.