"It was just kind of my time," Roberts told the Baltimore Sun. "There were numerous reasons that I felt like I couldn't play at a level that I was accustomed to and wanted to play at if I continued to play. I always said that I wasn't going to be the guy that tried to hang on as long as I could."
Roberts signed with the New York Yankees in 2014, but was released in August after hitting .237 in 91 games. He told the Sun that several teams had expressed interest in signing him, but he decided against a deal.
He ends his career with a .276 average, 97 home runs and 542 RBIs.
Baltimore's supplemental first-round pick in 1999 was among the players listed in the 2007 Mitchell report, with Roberts later saying he tried steroids only once, in 2003.
A two-time All-Star, Roberts said he did not speak with the Orioles about an extension after the 2013 season.
"I took, at the time, the best offer I had," Roberts told the Sun. "Do I wish in some ways that I had spent every day with the Orioles? Sure, that was a dream of mine for a long time. I don't think I ever shied away from making that pretty clear. It will always be the organization I feel like is home for me."