The 46-year-old businessman will replace Joan Laporta, who steps down at the end of the month, after gaining 61.35 percent of the vote against three other candidates Agusti Benedito, Marc Ingla and Jaume Ferrer.
Rosell collected 35,021 votes, the highest in the club's history after a record turnout, as Barca's 'socios' (club members) failed to rally behind Laporta's preferred successor Ferrer, who came in last.
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"I will be a president for everyone. I know it's a position with a great deal of responsibility. I will not fail you," Rosell told a news conference.
Rosell has won favour despite Laporta having presided over one of the club's most successful periods since he took the helm in 2003, during which time they won two European Cups, four La Liga titles and a King's Cup.
Rosell has said he would offer coach Pep Guardiola a six-year contract and that he would like to turn him in to Barcelona's Alex Ferguson.
All candidates were in favour of pursuing Arsenal's Spain midfielder Cesc Fabregas, though Rosell had warned that he would not do so at any cost.
