Federer, the 2009 champion and this year's second seed, cruised to a 6-3, 6-3, 6-4 victory over Colombia's Alejandro Falla, while fellow Swiss star Wawrinka had little trouble in a 6-3, 6-2, 6-3 romp over Marsel Ilhan of Turkey. The fifth-seeded Nishikori also advanced in a 6-3, 7-5, 6-1 triumph over Frenchman Paul-Henri Mathieu.
Wearing pink shorts and a purple shirt, Federer was not broken on Sunday in a match that lasted just under two hours. He broke for a 5-3 lead in the first set, then broke serve twice in the second before finishing the match with one more break to improve to 8-0 all-time against Falla.
"I like the outfit. Let's enjoy color while we can," said Federer in a nod toward Wimbledon. "It's good to try to be fashionable in a city like Paris. You always want to make a statement. I think people enjoy it. I think it's powerful. We will see how many times I can wear it -- I hope seven matches."
Federer had his most uncomfortable moment after the match concluded, as a fan managed to run onto the court and tried to take a selfie with the 17-time Grand Slam champion.
"I'm not happy about it," said Federer, who said a similar incident occurred on Saturday as well. "Obviously not one second I'm happy about it. It happened yesterday in the practice, too."
Wawrinka, who could face Federer in the quarterfinals, made sure there was no repeat of last year when he fell in the first round at Roland Garros.
"I draw the lessons from my elimination last year, so I handled the match differently," said Wawrinka. "It's a new year, it's a new tournament, it's a new season, it's a new French Open."
Other early men's winners on a limited schedule Sunday included Spain's Roberto Bautista Agut, Germany's Philipp Kohlschreiber and Ernests Gulbis of Latvia.
Bautista Agut, seeded 19th, eased past Germany's Florian Mayer, 6-3, 6-1, 6-3, while the 22nd-seeded Kohlschreiber dropped just three games in a rout of Japan's Go Soeda. The 24th-seeded Gulbis picked up a 6-4, 6-4, 7-6 (7-3) win over Dutch veteran Igor Sijsling.
There was a minor upset, as Marcos Baghdatis of Cyprus eliminated 25th-seeded Ivo Karlovic in straight sets. Baghdatis will next play Bosnia's Damir Dzumhur, who advanced when Russian veteran Mikhail Youzhny was forced to retire after two sets.