"I was happy to get better swings at better pitches," said Rolen, who carried an 0-for-12 slide into the game. "I was not getting good swings in the St. Louis series."
Highly touted rookie Mike Stanton homered twice for Florida, which had won four straight.
Volquez (3-1), in his sixth start since coming back from Tommy John surgery, allowed one run and eight hits in six innings.
"Every time I pitch, I feel like I'm getting into a better rhythm and keeping us in the game," the right-hander said.
Johnson (10-5) pitched a season-low 3 2/3 innings while giving up a season-high 10 hits. His ERA went from a baseball-best 1.97 to 2.27.
"It was terrible all around," Johnson said of his 100th career start. "If I had to rank it, it would be close to the bottom. I was inconsistent. I made two good pitches, then left one up and they hit it. Everything feels good. I felt good in the bullpen."
Johnson finished with 92 pitches, just two fewer than Volquez, but that was due as much to the Reds as it was to Johnson, Florida manager Edwin Rodriguez said.
"JJ had a rough start," Rodriguez said. "We know and he knows that he has to make adjustments. He was behind in the count and went deep in the count. He was facing a very good hitting team that battles, and when you do that, you're going to find holes. It was a combination. It wasn't his best night, but he faced a very good hitting team."
Reds manager Dusty Baker served the first of his two-game suspension for his part in the bench-clearing brawl between Cincinnati and St. Louis on Tuesday. Baker watched from general manager Walk Jocketty's box while bench coach Chris Speier ran the club.
The Reds pounced on Johnson, scoring as many runs in the first inning as they had totaled against him in his previous three appearances against Cincinnati.
"Anybody will tell you that when you're facing those kinds of guys, you've got to get them early," Speier said. "That's the only way to beat those No. 1s."
Rolen hit the last of four consecutive first-inning singles, producing two runs. One out later, Bruce's bouncer up the middle took a bad hop off the glove of diving shortstop Hanley Ramirez and into center field, sending Votto home and making it 3-0.
"The most important thing is coming right back after the Cardinal series and going right to work," Bruce said.
Rolen also showed off his prowess on the basepaths in the third. The All-Star third baseman reached on a leadoff double and advanced to third on Jim Edmonds' grounder to second. Bruce then hit a chopper up the middle and Ramirez came home, but Rolen scored on a nifty slide past catcher Ronny Paulino.
Bruce led off the fifth with his 11th homer, a 419-foot shot to center field off Taylor Tankersley.
Stanton, who carried an 8-for-12 surge into the game, hit his 13th homer and second in two nights with one out in the sixth. He added a one-out homer to right in the eighth, despite struggling with a sore throat the past few days.
"My throat was the worst it's ever been this morning, but we switched up the medication and I took a nap in the training room before practice," he said. "I feel pretty good now."Notes
- The Marlins didn't reach their Cincinnati hotel until 4 a.m., about three hours later than expected, after beating Washington in a game that started almost two hours late and lasted almost 3½ hours.
- Edmonds went 0 for 4 to remain hitless in nine at-bats since joining the Reds in a trade on Monday.
- Cincinnati RHP Johnny Cueto decided to not appeal the seven-game suspension he received for his part in the Reds' brawl with St. Louis on Tuesday. RHP Homer Bailey is expected to come off the disabled list and start in Cueto's spot on Sunday.
- Highlights of the Cubs-Cardinals game in St. Louis were shown on the Great American Ball Park scoreboard in left field.