Esteban Granero struck to give Real the lead just before the break, Guti made it 2-0 in the 77th minute and Ronaldo wrapped up the victory in added time.
It was an emotional evening for the Espanyol players and fans as it was their first home league match since captain Dani Jarque collapsed and died last month and their first competitive game in their new Cornella-El Prat stadium.
Granero's goal came after he exchanged passes with Brazilian playmaker Kaka and finished past goalkeeper Carlos Kameni.
Ronaldo replaced the ineffective Karim Benzema and was on hand to slot into an empty net for Real's third.
Pellegrini told a news conference the poor state of the new pitch had made it difficult for the players and he had been impressed with Ronaldo's performances for his new club.
"Cristiano is adapting to the league and the team," he said. "To me, he seems very content."
SUPERB VOLLEY
At Getafe's Coliseum, Barca coach Pep Guardiola left Messi, Thierry Henry, Daniel Alves and fit-again Andres Iniesta on the bench and the European champions came under early pressure.
Valdes could only stand and watch again when an overhead kick from Roberto Soldado, who scored a hat-trick against Racing in Getafe's opening match, bounced back off a post.
Guardiola brought on Messi and Iniesta just before the hour and they took the lead almost immediately when Ibrahimovic stuck out a leg to steer the ball in off a post from Eric Abidal's deflected cross.
"Getafe fought for the ball today more than any team we have played since I became coach," Guardiola told a news conference. "Winning here is not easy and the victory is worth a lot."
Brazil striker Luis Fabiano netted twice and forward Diego Perotti scored a stunning drive in Sevilla's 4-1 win over visiting Real Zaragoza and Atletico Madrid were held 1-1 at home by 10-man Racing Santander.
