Spaniard Ferrer recovered from a slow start to defeat Japanese wildcard Takao Suzuki 4-6, 6-3, 6-2, while Roddick downed Austrian No.14 seed Jurgen Melzer 7-6 (2), 6-2.
Ferrer will next meet fifth-seeded Juan Martin Del Potro of Argentina, who defeated Jarkko Nieminen of Finland 6-1, 6-3.
The draw opened up for Roddick, as his likely quarterfinal opponent Jo-Wilfried Tsonga retired from his third-round match with a reported abdominal strain. The Frenchman, who reached the Australian Open final this year and won the ATP tournament in Bangkok last weekend, was leading 7-5, 1-2 when he was forced out. Serbian Viktor Troicki will meet Roddick.
Tomas Berdych of the Czech Republic defeated Tommy Robredo of Spain 7-6 (6), 6-2 and will face No. 3 Fernando Gonzalez of Chile in the quarterfinals. Gonzalez defeated American Amer Delic 6-4, 7-6 (4).
The other quarterfinal will be between Frenchman Richard Gasquet and German veteran Rainer Schuettler. The fourth-seeded Gasquet crushed Japanese Kei Nishikori 6-1, 6-2, while No.12 Schuettler lost an epic second-set tiebreak before recovering to edge Russian No. 8 Mikhail Youzhny 6-3, 6-7 (12), 6-4.
Ferrer broke Suzuki to go up 3-1 in the second set and said that was the key to winning the third-round match.
"It was a tough match, Takao surprised me,'' said Ferrer. "He was very focused but when I broke him in the second set I got more focused, then the third set was easier for me.''
Ferrer coasted through the final set and won with an ace to wrap up the match in 1 hour, 56 minutes.
Ferrer, currently No. 5 in the world rankings, defeated Gasquet in the final of the Japan Open last year.
He is coming off an opening-round exit in Beijing last week.
Roddick is coming off winning the China Open on Sunday and got through in three tiebreakers to defeat Ivo Minar in his opening match here Wednesday.
His third-round match against Melzer was much faster.
"I played OK,'' said Roddick. "Jurgen had a few calls go against him in the second set which is unfortunate, but I'm glad I didn't have to spend too much time on the court.''
Roddick broke Melzer to go up 2-1 in the second set. His return appeared to be long and Melzer was given a code violation for an audible obscenity after protesting.
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