Officially, the Detroit Lions signed two players on Friday, according to the NFL: wide receiver Naaman Roosevelt and center Sherman Carter. The signing of tight end Jordan Thompson, which was reported earlier, does not appear to be official just yet.
Like Thompson, both Roosevelt and Carter tried out for the Lions this week during their voluntary minicamp. Roosevelt previously spent time with the Buffalo Bills and Cleveland Browns, although he hasn't appeared in a game since 2011. That year, he had 16 catches for 257 yards and 1 touchdown.
Carter has even less experience. He was an undrafted free agent out of Tennessee State last year, and he spent part of the 2013 offseason with the San Francisco 49ers. He was let go in early August, though, and he didn't even get a chance to play in any preseason games.
As far as I can tell, the Lions will have 78 players under contract once the Thompson signing becomes official. If they use all eight of their draft picks this year, that will leave room for only four undrafted free agents unless some players currently under contract are released.