Roddick will play Luxembourg's Gilles Muller, who knocked off No. 8 Go Soeda of Japan 6-4, 6-3, for his 32nd ATP World Tour title on Sunday.
Isner was attempting to win his second straight event for the first time in his seven-year career, but fell short in Atlanta for the third straight year. He lost to Mardy Fish in the past two Atlanta finals.
Roddick, who has won nine of his past 10 matches, will team up with Isner as U.S. doubles partners when the Olympics begin next week at Wimbledon.
The first set was delayed 44 minutes after Isner took a 3-2 lead. When play resumed, Roddick won four of the next five games and won the set as Isner struggled with his forehand accuracy.
Andy Roddick, of the United States, returns a volley to Nicolas Mahut, of France, during the Atlanta Open tennis tournament on Wednesday night in Atlanta. / photo: Associated Press
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