The reigning European champions dominated from the opening stages at the Stadio Tre Fontane, scoring three times in the opening 54 minutes before adding three more goals in the second half. The victory leaves Barcelona as the only side on six points after the opening two league-phase matches.
Caroline Graham Hansen opened the scoring in the 19th minute with a trademark individual effort, carrying the ball forward before finishing superbly past Roma goalkeeper Rachele Baldi.
Barcelona doubled their advantage in the 39th minute when Shukurat Oladipo inadvertently turned the ball into her own net after Graham Hansen's attempted pass towards Clàudia Pina.
The visitors continued to dominate after the interval, with Pina making it 3–0 in the 54th minute after receiving a pass from Ewa Pajor.
Graham Hansen then completed her brace six minutes later, calmly finishing to put Barcelona four goals ahead.
Pina added her second of the evening in the 75th minute with a superb strike from the edge of the penalty area, before Ewa Pajor completed the rout in the 85th minute.
Goals
• Barcelona: Caroline Graham Hansen 19', Shukurat Oladipo own goal 39', Clàudia Pina 54', Caroline Graham Hansen 60', Clàudia Pina 75', Ewa Pajor 85'.
Barcelona's victory also saw Pajor make Champions League history. The Poland international's late goal was her 18th in the group stage/league phase of the competition, making her the leading scorer in that part of the tournament.
Graham Hansen was named Player of the Match after scoring twice, while her second goal maintained her remarkable record of never losing a Champions League match in which she has scored.
The result gives Barcelona maximum points from their first two league-phase fixtures and provides a major boost ahead of Sunday's Liga F Clásico against Real Madrid.