Pat Perez and Ian Leggatt were tied for fourth at 9-under-par 204 while Jerry Kelly was one shot further back at 8-under-par 205.
Smith, who is seeking his first win on the PGA Tour, has put together three solid rounds on the West Course at Westchester Country Club. The 32-year-old has posted two top-10 finishes so far this season.
'It has been a long day,' said Smith. 'Actually, I felt pretty good. I've played very similar all three rounds. I've hit a lot of fairways and I've hit a lot of greens and I've made some putts that I've needed to keep the round going.'
Smith was three shots behind Roberts to start the round and quietly crept up the leaderboard. He two-putted for birdie at the fifth to climb to minus 8 but ran into trouble three holes later with a bogey at the eighth after his second shot rolled into a bunker and he couldn't get up and down.
He recovered with a birdie at the very next hole and made it two in a row with a five-foot birdie putt at the 10th.
At the 13th, Smith landed his second shot 10 feet behind the hole and ran back the putt for a birdie to join a logjam atop the leaderboard at 10-under.
A total of four players were tied for the top spot on the back nine after Roberts ran into trouble with back-to-back bogeys from the ninth. Gossett, who reached 10-under with a birdie at the 10th, was joined by Kelly, who birdied the 11th to grab a share of the lead.
Perez was also tied for first after enjoying a brief two-shot lead. The 26-year-old torched the front nine for six birdies to reach 11-under but a double-bogey at the 12th dropped him out of the lead.
Perez, the 2001 PGA Tour Q-School medalist, recovered at the very next hole with a six-foot birdie putt.
Gossett took the outright lead with a birdie at the 14th but ran into trouble with a bogey at the 16th. Meanwhile, Kelly and Perez also faltered with bogeys.
Smith persisted and took sole possession of first at the par-5 last. He reached the green with his second shot and two-putted for birdie from 40 feet for his first career 36-hole lead.
'The whole reason that I play is to try to win,' said Smith. 'I've played out here 5 1/2 years, and I feel like each year I've gotten a little bit closer to being able to do that. If I could win tomorrow, it would be great. It's something that I've worked for for a long time, and it would be great.'
Gossett, who earned a breakthrough victory at last year's John Deere Classic, has yet to finish in the top-10 in 2002. The 23-year-old carded a one-under 70 to finish alongside Roberts at 10-under-par 203.
'All in all, I feel like I'm improving,' said Gossett. 'So ultimately, I'm really happy and that's what I'm after, is to be more steady and consistent.'
Hal Sutton is also looking for his first top-10 of the season. The 44-year-old has put himself in position for a good finish with a round of 4-under 67 Saturday to move to 7-under-par 206. He was joined by David Toms.
Stephen Ames, Stewart Cink and Jose Coceres were tied for ninth at 6-under-par 207.
Defending champion Sergio Garcia struggled early with three bogeys over his first four holes but recovered to finish with a round of 1-under 70. Garcia moved to 5-under-par 208 alongside Bryce Molder, Briny Baird, Tom Lehman and Peter Lonard.
Full-field scores from the Buick Classic