Roth didn't make his season debut until Nov. 1 after beginning the season on the Non-Football Injury list and then saw only limited action.
Still, Tuesday's move has to be considered a surprise considering Roth started at strongside linebacker last season.
The two additions to the active roster are cornerback Evan Oglesby and defensive end Ikaika Alama-Francis.
Oglesby has spent three of his four NFL seasons with Baltimore, but he was in Dallas in 2007 when Tony Sparano was an assistant there.
Alama-Francis, a teammate of Davone Bess at Hawaii, was a second-round pick of the Detroit Lions in 2007. He made two starts in 19 games with the Lions over two seasons.
The Dolphins also officially announced the placement of Jason Ferguson on injured reserve as well as the release of safety Nate Ness after he was on the active roster for one game.
Matt Roth's 2009 season has been strange, to say the least, and it took another unexpected turn on Tuesday. While announcing the signing of two new players, the Dolphins also revealed they had released the veteran linebacker.