The move will shift veteran signal-caller Fitzpatrick, who started the Dolphins' first two games of the season, to the bench. He completed only 50 percent of his passes and threw one touchdown to four interceptions.
Rosen will become the 21st quarterback to start for Miami since the retirement of Pro Football Hall of Fame passer Dan Marino in 2000. During that span, only the Cleveland Browns (29) and Chicago Bears (23) have had more quarterbacks to start a game.
Rosen appeared in garbage time in both of the Dolphins' blowout losses this season. He completed 38.1 percent (8-of-21) of his throws for 102 yards with two interceptions.
The Dolphins acquired Rosen, the No. 10 overall pick in the 2018 draft, in a trade with the Arizona Cardinals in the off-season. In the deal, Miami sent two draft picks to the Cardinals, who selected Kyler Murray with the No. 1 overall pick in the 2019 NFL Draft to replace him.
With the Cardinals, Rosen posted a 3-10 record in 13 starts last season. He completed 55 percent of his passes for 2,278 yards, 11 touchdowns and 14 picks.