The top-ranked McIlory closed with a 3-under 69 to finish at 21-under 267, shattering the tournament record by five strokes. He entered Sunday with a four-stroke lead over Simpson after a course-record 61 on Saturday.
“I'm really happy with my game and everything is firing on all cylinders,” McIlroy said.
Rodgers, playing on a sponsor exemption, was the only player to mount a serious challenge, getting within three shots after a birdie at No. 15. He finished with a 68, and Simpson shot a 72.
It is McIlroy's second victory in the past three weeks and his 11th on the PGA Tour. He won the Match Play Championship this month in San Francisco.
He has six top-10 finishes in his last eight PGA Tour starts.
“It's impressive,” Phil Mickelson said about McIlroy's tournament.
McIlroy reached 20 under on No. 12 when he knocked his approach shot from 132 yards to 2 feet of the cup for a tap-in birdie and it looked as if he might coast the rest of the way.
But Rodgers, who earned his first top-25 finish on the PGA Tour, made it interesting when he played a seven-hole stretch in 6-under par, sparked by an eagle on the par-5 10th hole. But McIlroy didn't flinch when Rodgers drained a 15-foot putt on No. 15 to pull within three shots of the lead.
Instead, McIlroy countered by rolling in a birdie putt on his own on No. 14, moving to 21 under and regaining a four-shot cushion.
Jeff Maggert won the Regions Tradition for his first Champions Tour major title, beating Kevin Sutherland with a 3-foot par putt on the first hole of a playoff.
Sutherland two-putted for bogey to set up Maggert for the winning shot on the 18th hole at Shoal Creek in Birmingham, Ala.
Maggert closed with an even-par 72 to match Sutherland at 14-under 274. Sutherland had a 71.
Maggert's only previous Champions Tour win came in Mississippi last year in his first start on the 50-and-over tour. He won three times on the PGA Tour, the last in the 2006 St. Jude Classic.
Sutherland had his second runner-up finish of the year and remains stuck at one career win in 544 tournaments spread across the PGA, Champions and Web.com tours.
James Morrison of England won the Spanish Open by four shots after shooting a 3-under 69 at Terrassa, Spain.
Morrison entered the day tied for the lead with David Howell and pulled away by making three birdies while not dropping a shot at the Real Club de Golf El Prat. He finished the tournament on a total of 10-under 278.
It was the 30-year-old Morrison's second career win on the European Tour, and the “In years past when I haven't done it it's been too much looking at leaderboards and outside influences, and today … (I) stuck to my process all day long and executed, which feels amazing,” Morrison said.
Defending champion Miguel Angel Jimenez rose into a tie for second after the Spaniard eagled the fourth hole en route to a 67. Howell (73), Francesco Molinari (71) and Edouard Espana (69) also shared second.