41 former Trojans will being the 2015 NFL season on an NFL roster. The Bills, Cardinals, 49ers, and Vikings each have three former Trojans while seven teams have none.
Arizona Cardinals: QB Matt Barkley, QB Carson Palmer, DE Frostee Rucker
Atlanta Falcons: LB Allen Bradford
Baltimore Ravens: RB Javorius "Buck" Allen
Buffalo Bills: QB Matt Cassel, CB Nickell Robey, WR Robert Woods
Carolina Panthers: DE Wes Horton, C Ryan Kalil
Chicago Bears: None
Cincinnati Bengals: LB Rey Maualuga, CB Josh Shaw
Cleveland Browns: Hayes Pullard (practice squad) TE Randall Telfer (reserve, non-football injury)
Dallas Cowboys: LT Tyron Smith
Denver Broncos: DT George Uko (practice squad)
Detroit Lions: None
Green Bay Packers: LB Clay Matthews, LB Nick Perry
Houston Texans: LB Brian Cushing
Indianapolis Colts: C/G Khaled Holmes
Jacksonville Jaguars: WR Marqise Lee
Kansas City Chiefs: None
Miami Dolphins: TE Jordan Cameron
Minnesota Vikings: TE Rhett Ellison, DE Everson Griffen, LT Matt Kalil
New England Patriots: None
New Orleans Saints: None
New York Giants: LB Devon Kennard
New York Jets: DE Leonard Williams
Oakland Raiders: LB Malcolm Smith
Philadelphia Eagles: WR Nelson Agholor, QB Mark Sanchez
Pittsburgh Steelers: TE Xavier Grimble (practice squad)
St. Louis Rams: SS T.J. McDonald
San Diego Chargers: None
San Francisco 49ers: RB Reggie Bush, C Marcus Martin, CB Shareece Wright
Seattle Seahawks: SS Dion Bailey, LB Mike Morgan
Tampa Bay Buccaneers: None
Teneesse Titans: DT Jurrell Casey, DT J.R. Tavai (injured reserve)
Washington Redskins: TE Anthony McCoy, RB Silas Redd Jr. (injured reserve)
Here is more information about USC's rich history in the NFL from usctrojans.com.