Bryant had been with another high-powered agent, Eugene Parker, but decided to make the change.
Rosenhaus represents Cowboys cornerback Mike Jenkins and wide receiver Kevin Ogletree. He also negotiated safety Abram Elam's one-year contract with the Cowboys after the lockout. Rosenhaus doesn't represent Elam any longer.
Rosenhaus was spotted in the Cowboys players' parking lot on Monday afternoon.
Bryant did not respond to a text message seeking comment.
Bryant said last week he was thinking of changing agents and that it was a difficult decision because he valued Parker, who negotiated his rookie contract in 2010 and he was able to give him mentors to speak with during his rookie season.
In 2011, Bryant is second on the team with 57 catches for 858 yards and nine touchdowns.
Calvin Watkins covers the Cowboys for ESPNDallas.com.