After withdrawing from last week's Barcelona Open, Nadal appeared fresh and dictated play with his usual combination of heavy topspin, few unforced errors and baseline winners. The third-ranked Spaniard improved to 6-0 in his career against his 29th-ranked German opponent.
"It wasn't my best match, but I did well," Nadal said. "I played safe and I played focused all the time. Philipp made more mistakes than usual."
Federer got some consolation Wednesday when he teamed in doubles with fellow Swiss player Yves Allegro to beat sixth-seeded Simon Aspelin of Sweden and Paul Hanley of Australia 4-6, 6-3, 10-8 after a champions tiebreak.
In other matches, American John Isner lost to Brazilian Thomaz Bellucci 7-6 (7), 7-5; Jo-Wilfried Tsonga cruised past Viktor Troicki 6-2, 6-3; and Ivan Ljubicic eliminated Nicolas Almagro 7-5, 7-6 (3).
Nadal only faced one break point in his match -- at 2-3 in the second set -- and saved it when Kohlschreiber missed an easy backhand wide. Nadal broke in the next game, producing a high passing shot that Kohlschreiber could barely get his racket on, and cruised the rest of the way.
The new 10,500-seat stadium at the Foro Italico was nearly full for the match, but Nadal gave the spectators only 1 hour, 10 minutes of play. He led 18-15 in winners and committed only 11 unforced errors to Kohlschreiber's 28.
Nadal's dominance was similar to when he won the Monte Carlo Masters two weeks ago, dropping only 14 games in five matches and routing Fernando Verdasco 6-0, 6-1 in the final.
With Nadal absent, Verdasco won his fifth career title in Barcelona last week. He edged Simone Bolelli 7-6 (11), 6-3 to open his campaign in Rome.
Also, Stanislas Wawrinka eliminated Tomas Berdych 2-6, 6-3, 7-6 (6) and 42nd-ranked Guillermo Garcia-Lopez beat former No. 1 Lleyton Hewitt 6-2, 6-3. Filippo Volandri stopped Julien Benneteau 6-2, 6-0, while Santiago Giraldo beat Michael Llodra 6-3, 6-2.
Soderling was coming off a runner-up finish at the Barcelona Open, where he lost to Verdasco in three sets. In the Swede's previous two tournaments -- Masters Series events in Indian Wells and Key Biscayne -- he reached the semifinals.
Soderling ended Nadal's perfect record at the French Open last year and is in the same quarter of the draw as the Spaniard.