Showing no sign of the knee problems that sidelined him at the end of last year, Nadal yielded only eight points in six games in the first set. When Rochus finally got on the board while already down a break in the second, the capacity crowd in Rod Laver Arena gave him a huge ovation.
Nadal, who reached the semifinals here last year and is seeking his sixth Grand Slam title, finished with 47 winners to just seven for Rochus and also blasted 10 aces. The 75th-ranked Belgian, who fell to 13-31 in Grand Slam play, managed to laugh several times, realizing there was little he could do.
Nadal broke for the seventh time to pull ahead 5-2 in the final set, then held at love with four winners to finish off the victory in 77 minutes.
Conditions were perfect for the last match of the night, a sharp contrast to the brutal sun and swirling winds that plagued players earlier in the day.
Serena Williams also had to deal with a slight head cold, but she had no problem in a 6-3, 6-2 victory over 123rd-ranked Yuan Meng of China to begin pursuit of her 10th Grand Slam title. Yuan was all but ducking for cover from an onslaught of powerful serves, groundstrokes and volleys from the second-seeded American.
And get this: Williams wasn't even going all out.
"It was a little hot for me today," said Williams, aiming to keep intact her record of winning here in odd-numbered years since 2003. "But I was able to just take my time and play a lot slower, not giving 1,000 percent.
"I think it was pretty important for me not to ... go crazy out there, try and conserve some energy. Keep in mind, I am playing doubles here, as well. I definitely want to do well in both events."
That would be doubles with sister Venus - the reigning Wimbledon champion - who overcame a lapse against hard-hitting Angelique Kerber of Germany to advance with a 6-3, 6-3 victory.
While the Williams sisters were happy to get through without any drama, Britain's Andy Murray wished he had spent more time in the sun. The 21-year-old Scot got a mixed blessing when Andrei Pavel, who was hoping to make a farewell tour of the majors before retiring, had to quit after 45 minutes when his bad back acted up.
"I would have liked to have been on court a bit longer," said the fourth-seeded Murray, who won for the first time on center court here. "You don't want to win a match like that."
Most everybody else was eager to finish fast with the temperature topping 104 degrees in the afternoon. Murray said he could feel his feet burning on long points. Photographers at courtside draped their heads, bodies and cameras in wet towels. Spectators fanned themselves with paper and official programs.
"It was definitely extreme conditions," Serena Williams said.
A cool front came through and conditions were a pleasant 79 degrees by the time sixth-seeded Venus went on court. It turned into essentially a good hitting session for her.
"I was really happy to be able to be out there and hit a lot of balls and find a rhythm and advance," she said.
Olympic gold medalist Elena Dementieva beat Germany's Kristina Barrois to extend her winning streak this year to 11 matches. Also advancing were No. 13 Victoria Azarenka of Belarus, 2006 champion Amelie Mauresmo of France and No. 22 Zheng Jie of China.
No. 9 Agnieszka Radwanska of Poland became the highest seeded player to be ousted, falling to Ukraine's Kateryna Bondarenko.
On the men's side, No. 5 Jo-Wilfried Tsonga beat Argentina's Juan Monaco, No. 6 Gilles Simon downed Spain's Pablo Andujar and fellow Frenchman Richard Gasquet, seeded 24th, ousted Diego Junqueira.
Tsonga had upset wins over Murray in the first round and Nadal in the semifinals here last year before losing the final to Novak Djokovic.
Ninth-seeded James Blake, who reached the quarterfinals at Melbourne Park last year to match his best effort at a Grand Slam, had more than twice as many winners as unforced errors while beating Canada's Frank Dancevic.
No. 13 Fernando Gonzalez of Chile, runner-up here to Federer in 2007, ended local hope Lleyton Hewitt's 13th Australian Open. Hewitt, a former U.S. Open and Wimbledon champion, lost the final at his home major in 2005 to Marat Safin.