With temperatures in the 50s and winds gusting up to 30 mph., the field's scoring average soared to 80.119 on the par-71 course. That is the highest single-round scoring average in Champions Tour history.
This was also the first time since the 1982 U.S. Senior Open at Oakland Hills Country Club that not one player shot par or better.
Des Smyth and Craig Stadler each shot 2-over-par 73 on Thursday to share second place. They were joined there by Giuseppe Cali, Ray Stewart, Frank Connor, Derrick Cooper and Terry Gale.
Mark James, who won the The ACE Group Classic earlier this season, shares ninth place with Alan Tapie at plus-3.
Roberts got off to a good start with a birdie at the first from the back fringe. He tripped to a three-putt bogey at the next, but the eight-time winner on the PGA Tour bounced right back to drain a 50-foot birdie putt on the third.
The 50-year-old stumbled to bogeys on the fifth and seventh to fall to plus-1. Roberts double bogeyed the ninth, but came back with a birdie on 10.
Roberts moved back to plus-1 with a birdie on the par-5 12th after he pitched his third to 4 feet. He got to even par with a birdie on 13 but tripped to the fourth bogey of his round at the 15th.
He got that shot back with a 6-foot birdie putt on the par-4 16th and then tripped to a bogey at the last to finish at plus-1.
'The first nine was brutally tough,' said Roberts. 'And I got off to a very good start, considering the weather and all that. I played pretty solid the front nine. Made a couple of bogeys that I shouldn't have. But it's going to happen today. After a hiccup on nine, I played really solid coming home.'
Smyth got off to a rough start with bogeys on the first and third. He fell even further down the leaderboard after a double bogey on the par-4 fourth.
The Irishman bounced back with a birdie on the fifth. Smyth got another stroke back when he sank a birdie putt on No. 7, but he made the turn at plus-3 after a bogey at the ninth.
Smyth, who has won twice on the Champions Tour this season, heated up on the back nine. The 52-year-old birdied the par-5 12th and got to plus-1 with a birdie on the 15th.
The two-time Ryder Cupper got to even par as he birdied the par-4 16th. Smyth, however, faltered to a double bogey at the last to end at plus-2.
Stadler played well in the tough conditions as he opened with five straight pars. He then rolled in a birdie putt on the sixth. The reigning JELD-WEN Tradition champion then stumbled to consecutive bogeys from the eighth.
Around the turn, Stadler got back to even par with a birdie on the 10th. The 52-year-old dropped to plus-2 after bogeys on 11 and 13 and then closed with five straight pars.
Tom Watson, a five-time British Open champion, opened with a 4-over-par 75. He was joined in 11th place by Eduardo Romero, Isao Aoki, Carl Mason, Tony Price, Horacio Carbonetti, John Chillas and Doug Johnson.
Price and Nick Job (plus-5) each aced the par-3 third and were awarded 223 bottles of Hardys wine for the feat.
Greg Norman, who is also making his Champions Tour debut, is tied for 19th with Job at 5-over-par 76.
Defending champion Pete Oakley struggled to an opening-round, 11-over-par 82.