At the age of 31, Fabricio Oberto holds the record for oldest rookie in the NBA. Oberto played for the San Antonio Spurs.
Dwanye Rolson at 33
Ben Goldfaden was 33 when he played as a rookie in the ABA for the Washington Capitols in 1946. However, since the NBA-ABA merger, Antoine Rigaudeau was the oldest rookie. He was 31 when he played as a rookie for the Dallas Mavericks in 2002-2003.
A man by the name of Jim Morris. You may know him from the Disney film "The Rookie".
Saverio Rocca (P) Eagles he was 33...
Brandon Weeden. He was 28 when he was drafted.