Edwin Encarnacion was part of a package of three players the Reds gave up to acquire Rolen, who is batting .320 with eight homers and 43 RBIs. They also sent right-handed reliever Josh Roenicke and a minor leaguer to the Blue Jays, who included cash to cover part of Rolen's salary.
Rolen has one more year left on an eight-year, $90 million deal he signed with St. Louis. Former Cardinals general manager Walt Jocketty made it a priority to get Rolen.
"He will bring a lot to this ballclub that's been lacking," said Jocketty, in his second season as the Reds GM. "He brings leadership. He's a veteran. I think he'll add a lot to this club. And he's still playing well. He's a good RBI man and a Gold Glove at third base."
The 34-year-old Rolen is a five-time All-Star. He was the 1997 NL Rookie of the Year with Philadelphia and helped St. Louis win the 2006 World Series.
Rolen clashed in St. Louis with manager Tony La Russa after the 2006 playoffs, when the third baseman was benched. Rolen later requested a trade. He waived a no-trade provision in his contract to go to Toronto in January 2008.
"He mentioned he's got some personal things he's dealing with and if we could move him to a spot closer to his home, if we would take that into consideration, and we did," Toronto general manager J.P. Ricciardi said. "It ended up working out really well for us."
Rolen grew up in Evansville, Ind. He'll assume the spot that the Reds hoped Encarnacion would fill for years to come. Instead, the 26-year-old Encarnacion was an inconsistent hitter and erratic fielder.
Encarnacion led the team in errors last season with 23, and missed two months of this season with a chipped bone in his left wrist.
Encarnacion is batting .209 with five homers and 16 RBIs. He'll make $4.75 million in 2010, the final year of his contract.
Encarnacion declined to talk to the media after the trade.
"It could be a good move for Edwin, too," manager Dusty Baker said. "Sometimes a change of scenery is good for you."
Roenicke didn't have a record in 11 appearances with the Reds. He had a 2.70 ERA in two stints with Cincinnati this season. The Blue Jays also got right-hander Zach Stewart, who started the season at Class A and was eventually promoted to Triple-A Louisville, where he had two saves in nine appearances.
Hairston gives the Yankees a versatile player who has appeared at six positions this season. Hairston is batting .254 with eight homers and 27 RBIs, having played shortstop, second base, third base and all three outfield positions this season.
Information from The Associated Press was used in this report.