Compensatory draft picks are usually awarded following the third rounds and are based on the specific player lost to another team. The Baltimore Ravens lost four players last year that are expected to return the team's investment as draft picks this April, according to Jimmy Kempski of Blogging The bEast, who also contributes to SB Nation's Philadelphia Eagles blog, Bleeding Green Nation.
Kempski's detailed research explains the process for determining the round position that is awarded for the Compensatory Picks. He sees the four players lost by the Ravens last year resulting in single picks at the end of the 4th, 5th, 6th and 7th rounds.
The 4th round pick is in return for guard Ben Grubbs signing with the New Orleans Saints. The 5th round pick is in return for OLB Jarret Johnson signing with the San Diego Chargers. The 6th round pick is in return for DE Cory Redding signing with the Indianapolis Colts and the 7th round pick is in return for losing safety Tom Zbikowski, also to the Colts.
Remember, these are just his projections and will not be written in stone until the NFL makes it official as we get closer to April's draft.