In the women's event, former champion Lindsay Davenport continued her assault on her third title, fighting off three second set points to defeat French 19th seed Natalie Dechy 6-2, 7-6 to reach the final.
Volleying brilliantly and capitalising on Roddick's weaker backhand, the ninth-seeded Henman never folded mentally despite squandering 4-2 leads in the opening two sets.
"I'm more aware of my own game now," the Paris Indoors champion said after winning his 10th straight match at a Tennis Masters Series event.
"It's been a long process of learning to believe in myself and feeling relaxed out there, but I know I'm capable of playing very well."
Even though Roddick battled back from a break down to steal the first set with a cute forehand volley drop shot to win the tiebreaker, Henman never strayed from his game plan, which was to attack the Roddick backhand at all costs.
Henman raced out to a 4-2 lead in the second set, but Roddick broke back to 4-4 when the ninth seed dumped a forehand into the net.
Serving at 5-6, the Briton faced a match point but was able to power a 114-mph serve into the American's body that Roddick could not handle.
Henman played an almost perfect tiebreaker, while the U.S. Open champion uncharacteristically committed six unforced errors and managed to win only one point.
In a tense third set, Henman continued to press and converted on his third break point to lead 5-3 when the American pushed an easy
Henman, who reached the final here two years ago, served out the two-and-a-half hour match in impressive fashion, winning the contest when he clubbed a forehand crosscourt winner.
THIRD WIN
In beating Roddick for the third time in four matches, Henman ended the contest with 55 winners to 38, and won 52 of his 77 net approaches.
He next lines up against the winner of the James Blake-Irakli Labadze quarter-final later in the day.
Third seed Davenport has never lost to Dechy and appeared well on her way to victory up a break early in the second set, but the Frenchwoman battled back with a series of crosscourt blasts.
Dechy held three set points with Davenport serving at 5-6, but after the Frenchwoman missed a backhand return, Davenport crushed four straight winners, evening the contest with a 99-mph service winner.
"I played well when I was down. I really felt from that point on (the saved set points) I was able to step into the court more and dictate," Davenport said.
In an impressive tiebreak, Davenport made only one unforced error and ripped six winners, ending the contest when she buried a forehand into the corner and sent down a 105-mph ace.
Davenport will face either top-ranked Justine Henin-Hardenne or fifth ranked Anastasia Myskina in the final after the pair clash in the final match of the night.
"I'm really happy I've been able to break thorough and get to the finals again. I had a relatively easy draw but I was still able to come through," Davenport added.