The Pittsburgh Steelers' star quarterback met with Goodell early Friday and was told he could return on Oct. 17 against Cleveland.
Roethlisberger was suspended in April for violating the league's personal conduct policy, but Goodell said at the time he would review Roethlisberger's behavior over the next few months. Goodell was satisfied that the player has followed the league's guidelines and stayed out of trouble.
Roethlisberger was accused of sexually assaulting a Georgia college student following a night of drinking in a Milledgeville, Ga., bar on March 5. He was not charged by Georgia authorities.
The league said the "reinstatement is contingent on Roethlisberger continuing to adhere to the program established by our advisors and avoiding any further violations of the personal conduct policy."
"You have told me and the Steelers that you are committed to making better decisions," Goodell said in a letter to Roethlisberger. "Your actions over the past several months have been consistent with that promise and you must continue to honor that commitment."
Roethlisberger is the first player suspended by Goodell under the NFL's personal conduct policy who was not arrested, charged with or convicted of a crime. However, Goodell said in April the policy allows him to impose such a penalty when the league's integrity and reputation are at stake.
Roethlisberger's representatives at one point wanted the suspension cut in half, to three games, but Goodell stipulated in April it would be a six-game ban that could only be reduced to four games.
Steelers president Art Rooney accompanied Roethlisberger on his trip to see Goodell. Rooney and his organization kept in frequent contact with Goodell throughout the four-month process, during which Roethlisberger underwent extensive evaluations.
Indeed, Goodell's ruling was made in consultation with Rooney and the Steelers, who were angered by the two-time Super Bowl winner's behavior and would have punished him if the league hadn't.
Roethlisberger and Goodell met last month at the team's training camp in Latrobe, Pa. At that time, Goodell said he was encouraged by the progress Roethlisberger was making and promised to make his decision on the term of the suspension before the regular season began.
Goodell kept his word Friday.
The Steelers re-signed Byron Leftwich and planned to start him in Roethlisberger's absence. But Leftwich hurt his left knee in Thursday night's exhibition finale against Carolina. Depending on the extent of the injury, Pittsburgh could be down to Dennis Dixon and veteran Charlie Batch while Roethlisberger is suspended, and would certainly need to add another QB.
While he is out, Roethlisberger plans to work with a California-based quarterbacks coach, George Whitfield, and he'll throw to some free-agent receivers who are looking for work in the league.
Roethlisberger also is being sued in Nevada by a woman who says he sexually assaulted her there in 2008. No charges were brought in that case, and it did not figure in the NFL's suspension.