The Bengals Friday signed wide out Marcus Maxwell from their practice squad and waived wide receiver Courtney Roby. Maxwell was a seventh-round pick by San Francisco in 2005 and played in four games. He was on the 49ers’ practice squad last year and waived Aug. 28. The Bengals signed him to their practice squad Oct. 4. Roby signed with the Bengals on Oct. 16. He did not play Sunday against the Jets.  As for running back Rudi Johnson, he was once again not on the practice field Friday, and is now listed as doubtful for the game Sunday vs the Steelers.  Chad Johnson was back 100 percent for practice, and running back Chris Perry worked on the side getting set for practice next week.