Oliver, a Georgia cornerback, was picked 28th in the fourth round. The Ravens selected Gaither, a Maryland tackle, 31st in the fifth round. It marks the first time since 1998 that two players were taken in the supplemental draft.
"Jared has a chance to play in this league, even at a high level," Ravens general manager Ozzie Newsome said in a statement. "It would have been interesting to see how high he would have gone in the draft had he played one or two more seasons at Maryland."
Gaither started 17 of his final 21 games at right or left tackle as a freshman and a sophomore at Maryland.
Oliver was among Georgia's leaders with 57 tackles last season.
With the selections, San Diego and Baltimore will forgo the corresponding picks in the 2008 draft.