Scott, a first-round draft choice in 1997, became expendable when he lost his starting job to Willie Williams last season because of a quadriceps (thigh) injury.
Riemersma, who has played most of his eight-year career with Buffalo, was mainly a reserve for the Steelers last season. He did not play after a season-ending Achilles injury Dec. 5 against Jacksonville.
Riemersma caught seven passes for 82 yards and two touchdowns. Scott had 29 tackles and one interception in 2004.
Scott, a former University of Maryland product, has more than 400 tackles, 19 interceptions and four touchdowns in 91 career games.
Pittsburgh decided it could not afford his expected $4.8 million salary for next season.