The second-seeded Scot has won 23 of his past 24 matches since mid-August, with the only loss coming to Rafael Nadal in the semifinals of the U.S. Open. He's attempting to win his third title in as many weeks.
Ferrer had a string of errors to drop the first-set tiebreaker in his match, but he cleaned up his game in the second set, striking winners off the forehand and backhand side to break Roddick twice.
The 15th-ranked American had an opportunity to go up early in the third, but he wasted three break points on Ferrer's first service game -- and never challenged the Spaniard's serve again.
Fifth-ranked Ferrer finished with 49 winners -- twice as many as Roddick. Both players had 11 aces.
"I thought the second and third sets he played at an extremely high level and served pretty well," Roddick said. "You know, you normally don't count on him making a lot of first serves, hitting aces. I felt like today he did that and got himself out of trouble a couple of times."
Ebden gave Murray a tough time at the start of the first set, matching powerful groundstrokes and using slices and drop shots to keep Murray scrambling. But Murray broke the Australian twice to close out the set and twice in the second set.
"I got quite tense compared with how I've been feeling for the last few weeks," Murray said. "I don't know exactly why that was. Sometimes that happens."
Nishikori will become the highest-ranked Japanese player in ATP tour history thanks to his win over eighth-ranked Jo-Wilfried Tsonga this week. Ranked 47th, he's projected to rise to No. 32 -- beating Shuzo Matsuoka's previous best of No. 46.
The 21-year-old Nishikori, who is coached by former top-10 player Brad Gilbert, is having his best season on tour, reaching one final and four semifinals. Nishikori, who roomed with Gilbert's son Zachary at the Nick Bollettieri Tennis Academy in Florida, said the instruction has been key to improving his game.
"He knows a lot of players. He teaches me, you know, how the top players play, how I need to play," he said. "So it is helping me a lot."
Murray was once coached by Gilbert, too.
"I learned quite a lot from him," Murray said, "and hopefully I'll be able to use some of the things I learned from him against Kei."
Roddick had beaten Ferrer in the fourth round of the U.S. Open, after Ferrer scored an emotional win over the American two months earlier in a Davis Cup match played in Roddick's hometown of Austin, Texas.
Ferrer was nearly out of the Shanghai tournament in the last round -- he had to fight off three match points against countryman Juan Carlos Ferrero before winning in three sets. With the victory, he became the fifth player to qualify for the ATP World Tour Finals next month in London.