Rossi was the mayor of Osasco for two mandates, from 1973 to 1977, and again from 1989 to 1993. He was the secretary of Education and Tourism from 1980 to 1981 in the state government of Paulo Maluf. He participated in the Brazilian Constituent Assembly of 1987, being the reporter of the Electoral System and Political Party subcommittees. After his time with the subcommittees, he penned a constitutional article that created elections for all levels of government, 90 days after the approval of the new constitution.[1] He voted against the creation of a two-round election system in municipal elections as he believed it would hurt his chances of being elected mayor again in Osasco, attempting to compromise by only allowing a run-off for cities with more than 500,000 people (Osasco during this time period had around 400,000 people).[2]
He ran to be the director of the São Paulo PMDB in 2009, losing to Orestes Quércia in a vote of 73 for Rossi and 600 for Quércia.
He ran to be the mayor of São Paulo three times, the first in 1984 under the small National Communitarian Party (PCN). He came in a distant fourth place. He attempted again for the position two times, in 1996 and 2004, without success. He ran for governor of São Paulo in 1994 and 1998, both times eventually losing to Mário Covas. His last municipal run was in 2012 to become mayor of Osasco again, gaining 14.38% of the vote. In 2016 and again in 2020, his wife Ana Maria Rossi was elected vice-mayor of Osasco, running with then-mayoral candidate Rogério Lins [pt]. She later ran for state deputy in 2022.[3]
In 2018, he was considered as a vice-gubernatorial candidate under then-governor Márcio França's run for election in his own right as governor of São Paulo.[4] He later became a state deputy candidate for that year's elections as well.[5]
During the 2022 general elections, he and his family endorsed Jair Bolsonaro for president and Tarcísio de Freitas for governor of São Paulo.[6]
