Roush confirmed the decision Sunday, a move that had long been expected but could not be substantiated because Edwards refuses to publicly discuss contract negotiations. He is believed to be headed to Joe Gibbs Racing in a new fourth car, but his contract with Roush does not permit him to announce his plans until September.
Matt Kenseth was bound by the same clause when he left Roush at the end of 2012 and had to wait months to announce he was moving to Gibbs.
Edwards, speaking two hours before the start of the Brickyard 400, said he has a completed deal with another team but is not ready to talk about it. He tried to limit his time discussing his departure from Roush because the start of Sunday's race was approaching.
"Right now, the mission is to win this championship, this race," Edwards said. "This is my decision. It's a decision I made, and I didn't take it lightly. Sometimes you just want to make a change, and opportunities present themselves and you say, 'Hey, what was that like to not take that opportunity?'"
With a move to Gibbs, Edwards will be reunited at a Toyota team with Kenseth, whom he didn't always get along with when they were Roush teammates. Minutes before the race, team owner Joe Gibbs declined to discuss Edwards but said a fourth car at the organization is possible.
Leaving Roush ends Edwards' long association with Ford. The manufacturer stepped up heavily in contract negotiations four years ago to offer incentives to keep Edwards from leaving Roush for Gibbs.
"Carl Edwards has been a part of the Ford family for a decade, and it will certainly be tough to see him leave Ford and Roush Fenway Racing," said Jamie Allison, director of Ford Racing. "While we are disappointed in his decision to leave Roush Fenway Racing, we certainly want to extend our appreciation for Carl's contributions."
Edwards has been with Roush since 2003 and in the No. 99 Ford in the Cup Series since 2004. He has 67 career victories in NASCAR's three national series.
His results have not been anywhere close to what he had hoped after losing the 2011 championship on a tiebreaker to Tony Stewart.
Edwards went winless in 2012, his first year of a new three-year contract extension with Roush, and missed the Chase for the Sprint Cup championship. Although he won two races last season, he finished last in the 13-driver Chase field.
His performance is much better this year, and Edwards goes into Sunday's race at Indianapolis Motor Speedway ranked sixth in the standings with two victories. He said he does not want his departure to interfere with winning the Chase.
"If you look around, not in the NASCAR world but all of sports, change sometimes is a good thing from a performance standpoint," Edwards said. "You guys know what I've been through from a competitive standpoint. I've been really close as a driver to some championships, and I know what one point, one race can do. So the last thing I'm going to do or [the team] is going to do is let next year and beyond affect the championship."
Roush disclosed its three-driver 2015 lineup: Greg Biffle and Ricky Stenhouse Jr. will both return, and Trevor Bayne will move up from the Nationwide Series to a full-time Sprint Cup Series ride.
"We have always prided ourselves in developing talent at Roush Fenway, and our 2015 lineup is a testament to the success of our organization in that respect," Jack Roush said.
Biffle has been with Roush since 1998 and earned the organization its first NASCAR championship with the 2000 Truck Series crown. He added a Nationwide Series title in 2002.
He has qualified for the Chase in five of the last six seasons and was a career-best second in 2005.
"I don't have the words for what Jack Roush has meant to my career," Biffle said. "Our goal remains to run up front, win races and become the sport's first triple crown winner by having a championship in all three series."
Stenhouse, a two-time Nationwide Series champion, joined Roush Fenway in 2008. He replaced Kenseth in the No. 17 Ford when Kenseth left for Gibbs.
Fastenal, one of the primary sponsors on Edwards' car, will move its funding to Stenhouse next season to remain in the organization.
Roush officials had previously announced that Bayne will be promoted from the Nationwide Series to a full-time Cup ride next year, with AdvoCare as his primary sponsor of the No. 6 Ford.