Roddick, whose rigorous offseason training regime was designed to help him beat Federer and top-ranked Rafael Nadal, was in good form.
But second-ranked Federer outplayed him in every phase of the game. Ripping winners from all over the court and usually forcing Roddick to hit more than one good shot to win a point, he even had more aces than the hard-serving American, 16-8.
"I served well in the first set and that gave me a lot of confidence," Federer said. "I was moving well and getting a lot of balls back and making it difficult for Andy to get the upper hand from the baseline. That was kind of what I was hoping for."
Federer, seeking his fourth Australian title, will face the winner of Friday's semifinal between Nadal and fellow Spanish left-hander Fernando Verdasco.
"I don't have to wait to see who wins, I can start preparing for a leftie tonight,'' Federer said.
By the time Federer and Roddick were on court in the evening, temperatures had dropped to 33C (91F) so the retractable roof was open.
Although Roddick won their last meeting, Federer raised his record against him to 16-2.
"The last time I lost, so coming into this match there was a bit of pressure," Federer said.
It didn't show. Instead, this one played out like many of the Swiss star's previous victories.
Blunting Roddick's blistering serves, Federer broke twice in the first set. Adding to Roddick's frustration was a call that went against him as Federer served at 4-1.
A Federer shot was called out, but he successfully challenged. Chair umpire Enric Molina ruled that Roddick couldn't have gotten to the ball and gave the point to Federer. Roddick argued he stopped running when he heard the "out'' call, and he had an ongoing dialogue with Molina during several changeovers.
With both players holding easily in the second set, a tiebreaker loomed with Roddick serving at 5-5. Federer broke at love, then easily held with Roddick failing to get a serve return back in play. That was pretty much the match.
"Let's not kid ourselves," Roddick said. "You're down two sets to him and scraping, trying to survive. I hit the ball pretty well. He just came up with shots when he needed to. That's what he does."
Roddick had 38 winners, only 18 unforced errors and two double faults.
ALSO ON THIS STORY
Discuss: Sound off on tennis at Newsvine.comAfter serving a double-fault at 2-2 in the third set, Roddick got a warning for an audible obscenity and told Molina: "I take back the apology."
Roddick served again at 5-5 in the third set, and Federer - who seems to come up with his best tennis under pressure - broke again. He easily held, finishing off the match with a forehand down the line - his 51st winner to just 15 unforced errors and has been playing better with each match.
"Towards the end of the tournament, I think this is where you should judge a great player," Federer said.
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