Federer cruised past unseeded Russian Dmitry Tursunov 6-3 6-3 in only 58 minutes,
but former world number one Roddick needed 93 minutes to oust German qualifier
Simon Greul 6-3 3-6 6-2.
Federer will next face American James Blake, who defeated Argentina's Juan
Ignacio Chela 4-6 6-1 6-0.
It is a repeat of the Masters Series final in Indian Wells last Sunday, won
by Federer.
Tursunov, 23, had never faced Federer before but learned quickly why the "Federer
Express" is the defending champion and won January's Australian Open.
Federer won his 45th consecutive match in the United States and 21st Masters
match in a row.
"I always feel like it's more difficult to play somebody you haven't played," Federer
said. "We also haven't practiced, so you never get to know where he serves on
big points and stuff like this.
"But I feel I did very well. He's a very dangerous player and I really had
to play a solid game, and I thought I did, so I'm pleased."
Roddick, who fired nine aces and won 86 percent of his first-serve points,
qualifies for a quarterfinal against Spain's David Ferrer, who eliminated Belgian
Olivier Rochus 6-7 7-6 7-5
Roddick, who has reached only one semifinal in a disappointing year, took
the first set in 29 minutes, promptly lost the second, but dominated the decider,
breaking Greul in the second game on his way to victory.
"If I would have let it go a little further in the third set, he would have
had a lot of momentum and it would have been tough for me," Roddick said.
Greul had earlier ousted Thailand's Paradorn Srichaphan, Slovakia's Dominik
Hrbaty and Britain's Tim Henman, who blitzed the 25-year-old from Stuttgart
in the first set only to drop the last two.
Two Croatians also won fourth-round matches. Sixth seed Ivan Ljubicic defeated
Belgian Christophe Rochus 6-3 6-1 and Mario Ancic eliminated Russian fifth seed
Nikolay Davydenko 7-5 6-4.
Third-seeded David Nalbandian of Argentina will face Ancic after beating Czech
Radek Stepanek. Argentina's Agustin Calleri will play Ljubicic after downing
Nicolas Kiefer of Germany 3-6 6-3 7-5.
In the WTA event at the same venue, women's world number one Amelie Mauresmo
of France dispatched fifth-seeded Russian Nadia Petrova 6-, 6-1 to book a semifinal
date with Russia's Svetlana Kuznetsova.
The 2004 US Open winner ousted Japan's Ai Sugiyama 6-0 7-6.
