They can negotiate with other teams as of Sunday, but the Bengals will have the right to keep them by matching any offer. They can get a deal from another team up until May 2.
Hawkins missed the first half of last season with an ankle injury. He finished with 12 catches for 199 yards.
Sanzenbacher started one game and appeared in 10, getting six catches for 61 yards.
Rey played in every game and filled in when middle linebacker Rey Maualuga missed three games with a knee injury. He had four sacks, 54 tackles and two interceptions, one of which he returned for a touchdown.