Roberts, 28, had 45 receptions for 494 yards and two touchdowns last season, his fifth with the Raiders. He has 158 receptions for 1,826 yards and 13 touchdowns in 62 games, including 25 starts.
Perhaps the biggest plus with Roberts is his reputation for being an excellent downfield blocker. The Ravens have talked about how they were looking for receivers who can be physical in their run-heavy offense.
Bringing in Roberts doesn't preclude the Ravens from drafting a wide receiver as high as the first round at the end of the month.
The Ravens are familiar with Roberts, who scored the winning touchdown to beat them in September 2015. Roberts caught the go-ahead 12-yard score with 27 seconds remaining in a 37-33 win for Oakland.
This is only the second free-agent signing on the offensive side of the ball for Baltimore this offseason. The Ravens signed running back Mark Ingram last month.
Roberts was released by the Raiders on Thursday, one day after the team signed wide receiver Ryan Grant.
Roberts had been scheduled to receive a base salary of $4.45 million in 2019.