A supporter of Giovanni Giolitti, the statesman of Mondovì, Rosano was a member of Parliament representing the constituency of Aversa almost continuously from October 1882 to 1903, undersecretary at the Ministry of the Interior (1892–93) and Minister of Finance of the Kingdom of Italy in the Giolitti II Cabinet.

He was a prominent criminal lawyer whose penetrating and fascinating legal and oratorical style found success in all the courts of Italy and in the most difficult trials.

Rosano, unaccustomed to such bitter political clashes and experiencing serious family problems, proclaimed his innocence by shooting himself in the heart at his home in Naples, only six days after taking office as Minister of Finance.

[1][3][4] The city of Aversa named a street after him and erected a marble monument[5] in the Villa Comunale.

[1] Together with Giovanni Battista Cassinis, keeper of the seals from Piedmont, Rosano was the second minister who committed suicide in office since the foundation of the Kingdom of Italy.