D.A. Weibring carded a 3-under 68 to move into a tie for third at 8-under-par 205 and was joined there by Raymond Floyd, who won the PGA Championship at NCR in 1969. Floyd shot a 69 on Saturday.
Roberts tripped out of the gate with a bogey at the first after missing the fairway in the right rough. He got that stroke back with an up-and-down birdie on the par-5 sixth.
The eight-time winner on the PGA Tour then birdied the eighth from 7 feet out. Roberts bogeyed the ninth, after missing the fairway again, to make the turn at minus-9 and in a share of the lead.
Roberts, who made his Champions Tour debut last week, holed a 70-yard shot for eagle on the par-5 10th. After a bogey on 13, he still led by two. Roberts birdied 14 and 15, each from within 6 feet, to move three clear of Stadler.
The 50-year-old bogeyed 17 after his drive found the right rough and his second shot hit a tree and stopped short of the green in more heavy rough. That dropped him back to minus-11 as Roberts two-putted for par on the last to share the third-round lead.
'I didn't drive it as well today as I did the first couple of days, so I struggled and made a few more bogeys today,' Roberts said. 'Basically my whole round is capsulized in my third shot at 10 when I made eagle. Other than that, it was just kind of give and take all day.'
Stadler's round had a lot of movement to it. He bogeyed one and two, before getting one stroke back with a 5-foot birdie putt at the fifth. He two-putted for birdie on the 10th to join Roberts in the lead at minus-9.
The reigning JELD-WEN Tradition champion birdied the 11th from 8 feet out, but was down one after Roberts' eagle on 10. Stadler fell four off the pace with a double-bogey on 12 and a bogey at 13.
On 12, he drove it right, left his second in the rough and bounced his third over the green. Stadler then three-putted the 13th.
Stadler came roaring back with birdies on 14 and 15, both from within 10 feet. The 52-year-old closed with consecutive birdies from the 17th to join Roberts at minus-11.
'Obviously the back nine was just a yo-yo the whole way,' said Stadler. 'I made one par in nine holes, which was not ideal, but fortunately there was more good than bad. Momentum wise you always want to finish well, and after doubling 12 and bogeying 13, I dug a pretty good hole for myself and kind of regrouped and came back good. So hopefully that will carry over into tomorrow.'
Greg Norman, who also made his Champions Tour debut last week, posted a 2-under 69, that included two bogeys on the back nine, to end alone in seventh place at 6-under-par 207. Rodger Davis climbed the leaderboard with a 4-under 67 to take eighth place at minus-5.
Tom Jenkins (72), Wayne Levi (74), Jerry Pate (69) and Perry Arthur (66) share ninth at 4-under-par 209.