Federer appeared to be heading for his earliest grand slam defeat since 2003 when he struggled to find his touch for three sets on a damp day in Paris but found his range in the nick of time to subdue Argentina's Jose Acasuso 7-6 5-7 7-6 6-2.
Third seed William's second-round tussle was suspended on Wednesday due to bad light after she had lost the first set. She returned to save a match point before crawling over the finishing line with a 6-7 6-2 7-5 win over Czech Lucie Safarova.
Jelena Jankovic enjoyed an easier outing as she snuffed out the challenge of Slovak Magdalena Rybarikova 6-1 6-2 and Russian seventh seed Svetlana Kuznetsova was at her ruthless best in a 49-minute 6-0 6-2 demolition of Kazakhstan's Galina Voskoboeva.
Federer likes the sun to beat down on court so the clay plays faster but with the weather gods letting him down badly on Thursday, the Swiss world number two faced an uphill task against a player who feels at home on red dirt.
Despite the setback, Federer pulled through.
"It was a fun match to be part of," Federer told reporters.
"I was a bit lucky to come back in the third set. He was a double break up, there were not many shots he was missing and he was serving well.
"Once I won the third set, I had my grip on the match, I was stronger, physically and mentally."
Easy Victory
With little to analyse in yet another easy victory in Paris, fifth seed Jankovic did say she learnt something new from Serbia's President Boris Tadic when he made a flying visit to Roland Garros on Wednesday.
"He gave us some tips yesterday. Did you know if you eat fruit after the meal you get fat? I actually didn't know that," Jankovic told a bunch of amused reporters.
"If you eat it late in the afternoon or in the evening, it turns into fat. That's sugar."
While Jankovic has sliced through the draw, the Williams sisters have given the fans value for money.
Two days after Serena needed nine match points to huff and puff her way into round two, Venus saved a match point herself against the hard-hitting Safarova.
Safarova, no stranger to causing upsets, having beaten Amelie Mauresmo at the 2007 Australian Open when the Frenchwoman was defending champion, looked to have one foot in the third round when she had the long-limbed American lunging from side to side to earn match point at 5-4 in the third set.
But the American threw everything in her arsenal on the next point and stayed alive with a thumping forehand winner.
Two games later, the seven-times grand slam champion had her dad applauding on his feet when she streaked ahead to 40-0 to earn three match points.
She needed only one as Safarova's service return bounced on top of the net before rolling back to her side of the court to end a duel that had enthralled fans for two hours 30 minutes.
Men's fifth seed Juan Martin del Potro marched on by beating Serbia's Viktor Troicki 6-3 7-5 6-0, while 10th seed Nikolay Davydenko carved out a 4-6 6-3 6-0 6-2 win over Argentine Diego Junqueira.
French number one Marion Bartoli, the 13th seed, slumped to a 6-3 7-5 defeat by Italy's Tathiana Garbin.
