Roddick, the tournament runner-up the past two years, overwhelmed Grosjean in the third and fifth games of both sets to cruise to a 6-2, 6-2 victory.
He had won the title in 2001 and 2002.
"That was better than normal," said Roddick, a resident of nearby Austin, Texas. "To play well here year after year is great. To have your friends watching, your parents watching, it makes it special."
Roddick said he thought his forehand was a big difference in the match.
"I felt good, felt like I was really strong with my forehand," he said. "I put a lot of pressure on him with that shot."
Grosjean won just 50 per cent of his service points compared to 75 per cent for Roddick.
Roddick had 45 aces in four matches in claiming his 17th career title and second this year. He also won at San Jose.
The sixth-seeded Grosjean had upset second-seed Andre Agassi in the quarter-finals en route to his meeting with Roddick.
"Against the top guys, if you don't hold your serve and you're behind early, they don't let you in," Grosjean said.
"It was tough because today after my return he was hitting the ball so well"
Roddick said he was looking forward to the European claycourt season.
"I'm probably as confident as I've ever felt making that trip," Roddick said. "I'm excited."
