Federer, the top seed, put in a practise session with James Blake that was cut short by afternoon showers, after arriving at the Foto Italico at the weekend.
The Swiss superstar will make his start at the event, where he was upset a year ago in the third round by Italian Filippo Volandri, during a crisis period when Federer split with coach Tony Roche.
Canas ambushed Federer on successive weeks in March 2007 in Indian Wells and Miami, but Federer re-established the natural order with a win indoors seven months later in Madrid.
"I only look at who I play and who I might play if I win," Federer said. "You cannot change the draw, anyway."
Federer is off to a 9-1 start this season on clay, with an Estoril title and Monte Carlo final against Rafael Nadal, who arrived in the afternoon after winning a fourth straight Barcelona crown.
Against Federer, Canas won three of their previous five meetings on hard courts. The Rome showdown will be their first on clay.
Nadal flew into the Italian capital from Barcelona as he attempts to lift a fourth straight at the Foro Italico against either Juan Carlos Ferrero or Nicolas Kiefer.
"This year is a great one so far. I'm number one in the points race, and I've won two very important tournaments," Nadal said.
"For me, the important thing was to be playing well. I've been playing well during the last tournaments, and that's what I'm very happy about."
Richard Gasquet became the first upset victim, going out to a qualifier 6-4, 6-1, losing listlessly to Peruvian journeyman Luis Horna, dropping to a modest 2-3 record in Rome.
"Nothing happened today, I played my worst match maybe of the year," said one of nine Frenchman in the field. "Nothing happened on the court, I was lost."
Gasquet collapsed in exactly one hour on the clay, producing eight aces but not a single break point against his 27-year-old South American opponent, ranked 111.
"I didn't expect this match, for sure," Gasquet said. "I now have to forget it."
Croatian former clay threat Ivan Ljubicic continued a poor run of 2008 form as he was beaten in the first round by Belgian Steve Darcis 7-5, 7-6 (7-5).
Home players Potito Starace and Andreas Seppi advanced. Starace beat Croatian Marin Cilic 6-4, 2-6, 6-4 while Seppi stopped Frenchman Fabrice Santoro 6-4, 6-2.
France's Nicolas Mahut put out Italian qualifier Thomas Fabbiano in a 6-7 (5-7), 6-4, 7-5 struggle.