With top seed and five-time champion Nadal not on duty until Tuesday, seventh-seed David Ferrer led the Spanish charge, ably supported by veteran Ruben Ramirez Hidalgo, Guillermo Garcia-Lopez, Pere Riba and Albert Montanes.
Ferrer, the highest-ranked man on the wind-swept courts on Sunday, breezed past Finland's Jarkko Nieminen 6-3, 6-3, 6-1 to maintain his record of having never failed to get beyond the first round.
The 29-year-old, who was runner-up to Nadal on clay at Monte Carlo and Barcelona this year, will tackle France's Julien Benneteau for a place in the last 32.
"I always hope I get good performances in Paris. I think you need to take it step by step, one match after the other, because all matches are different," said Ferrer, twice a quarter-finalist.
Ramirez Hidalgo belied his 33 years to knock out Croatian 19th seed Marin Cilic 7-6 (7/5), 6-4, 6-4, the only male seeded casualty on the first day.
"The truth is that when I saw the draw, it wasn't very good for me, but I knew that with a little luck I'd win," said Ramirez Hidalgo.
Montanes saw off French lucky loser Marc Gicquel, who had replaced injured Australian former world number one Lleyton Hewitt in the draw, 6-4, 6-4, 6-2.
Hewitt had pulled out with a left ankle injury earlier in the day to hand Gicquel his chance.
"I was warming up to play against Hewitt and when I left to play it was Gicquel. He was difficult and complicated, but I played well," said Montanes, who now meets Ramirez Hidalgo.
Spain's Sunday success was completed by Riba, who beat Ivan Dodig of Croatia 6-3, 3-6, 7-6 (8/6), 6-4 and 30th seed Garcia-Lopez, a 6-1, 7-5, 4-6, 6-3 victor over Robert Kendrick of the United States.
Also making the next round were 14th seeded Swiss Stanilas Wawrinka, 17th-seeded Frenchman Jo-Wilfried Tsonga and Sergiy Stakhovsky, the 31st seed from Ukraine.
Japan's Kei Nishikori, with Andre Agassi's former coach Brad Gilbert in his corner, won the all-Asian battle with Taiwan's Lu Yen-Hsun, claiming a 6-1, 6-3, 6-4 win over last year's shock Wimbledon quarter-finalist.
The 21-year-old Japanese next tackles Stakhovsky.
Hewitt's pull-out was the latest injury setback for organisers after fellow former world number ones Andy Roddick and Juan Carlos Ferrero - the 2003 champion - were sidelined with right shoulder injuries.
Argentina's former Wimbledon runner-up David Nalbandian, Chile's Fernando Gonzalez, a 2009 Roland Garros semi-finalist, and four-time quarter-finalist Tommy Robredo are also missing from this year's event, which runs until June 5.
Serbian second seed Novak Djokovic, who is likely to depose Nadal as world number one over the next fortnight, begins his campaign on Monday against Dutchman Thiemo de Bakker.
Djokovic is undefeated in 2011, having won 37 straight matches.
Roger Federer, seeded three this year and the 2009 champion, takes on Spanish left-hander Feliciano Lopez in his Monday opener.
- AFPTags: sport, tennis, france