Robinson and Bell, who've both had problems off the field, were among 11 players signed by the Florida Tuskers on Thursday.
Robinson, who missed part of the 2006 and 2007 seasons while serving a one-year suspension for violating the NFL's substance abuse policy, was a first-round draft pick of the Seattle Seahawks in 2001.
In portions of eight seasons with the Seahawks, Green Bay Packers and Minnesota Vikings he had 294 receptions for 4,244 yards and 16 touchdowns. The 29-year-old was selected to play in the Pro Bowl as a kick returner in 2005.
Bell, 28, was drafted by the Denver Broncos in the second round in 2004. He was traded to Detroit in 2007, and his stay with the Lions ended badly when he was waived and later captured on camera removing two Gucci bags belonging to a teammate who was replacing him.
Bell re-signed with Denver last season, carrying 44 times for 249 yards and two touchdowns. In five NFL seasons, he rushed for 2,773 yards and 16 TDs.