"Just watching those guys battle back the way they did in the first game after being down like they were, that's huge," Lieber said.
First baseman Ryan Howard said the sweep "means we're on the up and up" in the wild-card race.
"Every game is important now," Howard said. "We have to keep the same mindset."
The sweep allowed the Phillies to gain one-half game on NL wild-card leader San Diego, which beat Cincinnati on Wednesday night. The Phillies are 1½ games behind San Diego.
"The first game when we came back kind of set the tone for the day, I think," said Phillies manager Charlie Manuel.
One day after their official elimination from the NL East race, the Braves' wild-card hopes took a serious blow as they fell 6½ games behind the Padres.
"That's not what we hoped for," said Braves manager Bobby Cox.
Lieber (8-9) has four wins and three no-decisions since his last loss on Aug. 5. He pitched 7 1/3 innings and allowed eight hits and two runs. He struck out two with no walks.
"I definitely feel I'm a much better pitcher than I was in April or May," Lieber said. "It's exciting. One reason I signed here is to help this ballclub get into the playoffs."
Rollins hit a two-run homer, his 20th, off Tim Hudson (12-11) into the Braves' bullpen in the second inning.
"I'm not going to say winning the first game made the second game easier, but it did give us momentum," Rollins said. "It put us on the right track."
Ruiz hit his third homer in the third. Ruiz, a rookie catcher, gave the Phillies a 5-1 lead with a run-scoring single in the fifth.
Adam LaRoche hit his 31st homer for Atlanta in the first inning, but Lieber then blanked the Braves before Brian McCann's 20th homer in the sixth inning.
In the Phillies' ninth, Abraham Nunez drove in two runs with a bases-loaded single off Joey Devine.
Overall, four Phillies relievers gave up no hits and three walks in seven scoreless innings. Eude Brito pitched four scoreless innings.
- Rollins' homer gave the Phillies their first double-play combination to each have 20 or more homers. Rollins has 20 homers and Utley has 28.
- Jones' double in the first game was the 300th of his career.