Cox, 27, was a free agent bust signing made by the Chargers last season. Cox received a four-year contract worth $20 million that included $10.25 million guaranteed from San Diego, but was released after one season.
He recently signed with the Ravens, but was among their final roster cuts.
Last year, Cox appeared in all 16 games, but totaled just 38 tackles and an interception. Pro Football Focus rated Cox as the No. 104 cornerback in the league out of 110 qualifying players last year.
Seastrunk was selected in the sixth-round of this year’s NFL draft by the Redskins. However, he was unable to make the final cut. Green Bay brought him for a visit earlier in the week.
Seastrunk was a five-star recruit coming out of high school, but he would later transfer to Baylor. He produced 2,189 yards rushing on 289 carries (7.57 YPC) and 18 TDs for the Bears over the course of two years.
Robinson, 24, signed with the Steelers as an undrafted free agent out of Temple back in 2012. He has since played for the Broncos, Chargers and Redskins.
Last year, Robinson appeared in eight games and recorded three tackles.