Pryor is most famous for his time at Ohio State. He got into trouble there for trading autographed memorabilia (your daily reminder that the NCAA is a crooked plantation system dressed up as a billion dollar corporation). He entered the supplemental NFL Draft, and the Oakland Raiders took him in 2011. The NFL suspended Pryor for five games over his role in the autograph scandal (because, NFL is also not a logical organization).
Pryor made 10 starts with the Raiders over three seasons with a 3-7 record. He has a total of 1,953 yards, nine touchdowns, 12 interceptions and a shaky 56.3 percent completion rate.
I'm not sure exactly what the Rams would see in Pryor, other than he does have the ability to make plays with his legs (576 rushing yards and two touchdowns last year for the Raiders). The offensive coaching staff's a poor track record developing players doesn't signal much hope for Pryor's long-term fortune in St. Louis, if the Rams were to sign him.