Goodell said on the Dan Patrick radio show the key issue is a "pattern of behavior" and "bad judgments."
Last week, prosecutors in Georgia declined to charge Roethlisberger after a college student accused him of sexual assault in March.
The NFL is expected to discipline Roethlisberger, although it says there is no timetable for such a decision. The Steelers have said they expect a decision next week.
Roethlisberger also is being sued by a different woman who says he raped her in 2008 at a Lake Tahoe hotel-casino. Roethlisberger denies the accusation and was not charged. He has claimed counter-damages in a lawsuit.
"The issue here is with respect to a pattern of behavior and bad judgments," Goodell said. "You do not have to be convicted or even charged with a crime to be able to demonstrate that you've violated a personal-conduct policy, and reflect poorly not only on themselves, but all of their teammates, every NFL player in the league, and everyone associated with the NFL. That is what my concern is, and I have expressed that directly to Ben, obviously, and I'll be making a decision as soon as I possibly can."
Roethlisberger practiced Monday for the first time since the season ended.