Second seed Nadal beat fellow Spaniard Fernando Verdasco 6-4 6-4, third seed Roddick overcame Olivier Rochus of Belgium 6-3, 7-6 and number 13 Murray crushed Frenchman Nicolas Mahut 6-1, 6-3.
Blake, runner-up to world number one Roger Federer last year, lost 6-2, 7-6 to Frenchman Julien Benneteau.
British number one Murray was cool and composed in searing heat, dominating from the back court and having little trouble returning Mahut's serve.
Murray served efficiently and his opponent threw his racket in frustration in the second set as he struggled to cope with the Scot's mixture of spin and pace.
"I played well," Murray told reporters. "He's got a big serve. He doesn't serve and volley as much but he's kind of tricky to play against. But at the baseline, he plays really aggressive off his forehand and only really slices his backhand.
"You have to play consistently. You don't want to go for big shots against somebody like him. You don't want to give him chances by making mistakes."
Murray will next play fourth seed Nikolay Davydenko of Russia who defeated Czech Jan Hernych 6-3, 6-1.
GOOD CHANCE
With Federer losing to Guillermo Canas on Sunday and former world number ones Lleyton Hewitt and Marat Safin also exiting the tournament, Murray thinks he has a good chance of winning the title.
"I'd say I'm one of the favorites," the 19-year-old said. "I take a lot of the guys, like Tommy Haas, Fernando Gonzalez, Nadal, Roddick, in front of me.
"You never know what happens in these sort of tournaments. Draws can open up. You just have to take your chances."
After completing his second-round victory at nearly midnight on Sunday, American Blake came out flat against Benneteau and never found his form.
"I didn't serve very well," Blake said. "I didn't return very well. I could have played better on the big points. I couldn't get a lot of momentum going. I don't know what happened. Just one of those days."
Benneteau will next face Serbian 12th seed Novak Djokovic who thrashed Russian Evgeny Korolev 6-2, 6-1.
Canas, who snapped Federer's 41-match winning streak in straight sets on Sunday, could not maintain his form against former French Open champion Carlos Moya of Spain, losing 6-4, 6-4.
Roddick will next face 15th seed Richard Gasquet of France, who defeated number 18 Jarkko Nieminen of Finland 6-3, 1-6, 6-3.
Chilean Gonzalez, the Australian Open runner-up, was a 7-6, 7-6 winner over Sweden's Robin Soederling, and number eight Ivan Ljubicic of Croatia beat Sweden's Thomas Johansson 6-1, 6-4.
