"I came out Thursday not knowing what I had," said former U.S. Open winner Rose, who made his first start since a surprising missed cut at the Masters.
"The whole week was a struggle if I'm dead honest but that makes the result more pleasing in a way, something I can build on.
"This was an important week for me. Three rounds in the 60s I'm pretty pleased on this golf course. Just not enough really good golf shots to challenge the leaders."
It was a different story for McIlroy, who trailed the leaders by two strokes overnight but finished eight behind Homa after shooting a two-over 73 for a share of eighth.
McIlroy has been in contention entering the final round almost every start on the PGA Tour this year but has only one victory -- at the Players Championship in March.
He ranks 93rd in final round scoring average (70.44 strokes)and does not exactly have a Tiger-like reputation for sealing the deal, despite his 15 PGA Tour victories and four major titles.
Poor putting brought McIlroy undone on Sunday, a three-putt par at the par-five seventh setting the wheels in motion.
He botched a pitch shot at the short par-four eighth to settle for par, and went bogey, double-bogey at the next two holes to become an afterthought down the stretch.
"Played first six holes well today, pretty steady and then the three-putt on seven derailed any momentum I had," the Northern Irishman told reporters.
"I hit a couple of drives left over the weekend but then my short game cost me a few shots, so I will go back home this week, work on that, get a bit sharper in those areas and get ready for a couple of weeks' time."
The PGA Championship, the year's second major, starts at Bethpage in New York on Thursday week.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Ian Ransom)
