He was born to Stanislao and Teresa Vianello in a house in calle degli Orbi, in the San Samuele district. The family was of wealthy conditions.
In 1907, together with his sculptor friend Arturo Martini, he went to Paris, where he was attracted by the painting of Gauguin (in addition to that of Van Gogh and the Fauves). Following in the footsteps of the painter from Tahiti, he then went to Brittany, which was a great discovery for him. He returned with some works includingthe famous painting The Flower Girl. Again with Martini he returned to Paris in 1912, where they exhibited together at the Salon de l'Automne, alongside Amedeo Modigliani. His first period, from 1908 to 1914, is underlined by a series of works executed in his stays in Burano (which for him and other Venetian painters constituted a kind of Brittany) and in Asolo. Breton landscapes, views of Burano and Asolan descriptions reveal different influences, from Gauguin's synthesis to certain liberty stylizations. But these works made of exciting color are contrasted by others in which the artist denounces a formal research of rigorous constructive commitment. Among these we remember Maternity, of 1913, The educator and Lady in green, of 1914. Called up to arms and sent to the front, he endured the drama of war to the end; the events of his imprisonment and particular family crises irremediably shaken his mental equilibrium. The return to his homeland and the new contacts with art opened to Rossi new visions and new directions, which led his painting towards Cubism, going back to the origins the lucid lesson of Cézanne. From 1918 to 1924 (a time when his illness worsened to lead him, in 1925, to the Sant'Artemio asylum in Treviso, from which he would only come out dead in 1947) he performed some works that place him, as later critics will recognize, among the greatest artists at the origin of modern Italian art.