The third-ranked Radwanska started the day by beating Maria-Teresa Torro-Flor 6-3, 6-2 for her second singles victory of the series, only for sister Urszula Radwanska to lose to Silvia Soler-Espinosa 6-1, 6-3 on the outdoor red clay at Barcelona's Olimpico Estadio.
That left the tie level at 2-2 and set up the doubles match where Agnieszka Radwanska and Rosolska beat Soler-Espinosa and Anabel Garrigues 6-4, 6-2.
The Polish pair fell behind a break at 3-4 down in the first set, but they roared back by winning seven straight games to claim the first set and build a commanding 4-0 lead in the second.
Earlier, Radwanska broke Torro-Flor seven times to win her second singles match in two days.
In the second reverse singles match, Soler-Espinosa hit seven aces and 27 winners to deal Urszula Radwanska her second loss in the tie.