Casillas is a fifth-year pro who spent the past four seasons with NFC South rival New Orleans. He started eight of 38 games he appeared in with the Saints, with three sacks and two fumble recoveries.
Ogletree was a backup with the Dallas Cowboys the past four seasons, appearing in 46 games and making 57 catches for 730 yards and four touchdowns.
The Bucs also announced deals to keep restricted free agent running back LeGarrette Blount, exclusive rights free agent defensive tackle Corvey Irvin and tendered restricted free agent defensive end Daniel Te'o-Nesheim.
The team also released linebacker Quincy Black, who missed the final seven games of last season after being injured while making a tackle.