Wide receiver Joe Hastings and defensive tackle Tracy Robertson, who both got tryouts with the Dolphins during this week's mini-camp, have been signed, the team announced Thursday. The Dolphins released wide receiver Courtney Gardner and fullback Ina Liaina. Hastings (6-0, 190), who played at Washburn (Kansas) University, a Div. II school, was undrafted in 2011 but made San Francisco's practice squad. He was on the active roster for three games in 2011, including two playoff games.