Rossi was a National Deputy for his native Santa Fe, and served as leader of the Front for Victory parliamentary bloc in the lower house.

In the 2005 legislative elections he ran for a seat in the Lower House of Congress for the Front for Victory, the largest faction of the Justicialist Party, formed by supporters of President Néstor Kirchner.

"[5] He also courted controversy with his rhetoric, notably in August 2010 when he described lawmakers who presented a bill that sought reverse a government decision to revoke an expired license for the Fibertel internet service provider, as "lawyers" for the Clarín Group (Fibertel's parent company); there have been ongoing controversies between Clarín and Kirchnerism since 2008 over a number of issues.

In the classical caudillist fashion that has prevailed in Argentina’s last century of politics, although some in the party, including Bielsa, would have rather negotiated on a consensus candidacy, Rossi insisted on conducting a primary election.

Rossi also stated that he wanted Bielsa's sister María Eugenia (then vice-governor of Santa Fe), on his party list, though he instead chose Jorge Fernández, former Minister of Education during the governorship of Víctor Reviglio.