His first government positions were as undersecretary for Public Works (1963-1966), Education (1966-1968 and 1970-72) and Interiors (1968-1969). Romita was subsequently three times Minister of Scientific Research in the Andreotti II (1972-1973), Forlani (1980-1981) and Fanfani V (1982-1983) Cabinets. In 1983-1984 he was also Minister of Regional Affairs (1983-1984) and Public Balance (1984-1987), respectively in the first and second Craxi governments.
Romita was national secretary of PSDI, succeeding Giuseppe Saragat, from 1976 to 1978. In 1989 he left the party and, together with Pietro Longo, he founded UDS (Moviment of Unity and e Socialist Democracy), later merged into PSI. He was Minister of Comunitary Policies in the Andreotti VII Cabinet Ministro. After the disbandment of PSI, he entered the newly formed Italian Socialists and then, from 1997, the Democratic Party of the Left.