Jankovic broke her to open the second set, and again to take a 3-0 lead en route to the victory.
Petkovic was pleased with her effort, and said she expected to be fit for the US Open, which starts in New York on August 29.
The win gives Jankovic a chance for her first title of 2011 at a tournament where she triumphed in 2009.
"It means a lot to me to be in the final again here," said Jankovic, runner-up in Monterrey in her only other final appearance this year.
Sharapova will be vying for a second tournament title this season to go with a triumph in Rome.
The three-time grand slam champion reached the final last year, falling to Kim Clijsters.
"I love playing on this court," Sharapova said. "There's something about it."
But the fourth-seeded Sharapova got off to a sluggish start against the second-ranked Zvonareva.
A welter of unforced errors by Sharapova helped Zvonareva break serve twice to take a 5-2 lead. Sharapova won just 11 points in the first seven games.
She managed to break Zvonareva to prolong the set, but Zvonareva broke back to pocket the frame.
After a court-side pep-talk from her coach Thomas Hogstedt, Sharapova was able to turn things around and secure her finals berth in two hours and tow minutes.
She adopted a more aggressive style to start the second set and broke Zvonareva in the opening game.
Under pressure, Zvonareva double-faulted to lose the second set and another double-fault from Zvonareva gave Sharapova a 3-1 lead in the third.
Two double-faults from Sharapova saw Zvonareva narrow the deficit to 4-3, but Sharapova recovered and punched a forehand winner down the line to take a 5-3 lead.
She served it out without drama, capping the match with another strng forehand and throwing her arms in the air in delight.
- AAP
