'I can't explain my thoughts right now,' said Rosales, who earns $240,000 for the win. 'It has not sunk in yet. I'm just so happy.'
Jung Yeon Lee matched Rosales' 65 to climb into second place at 13-under-par 275. She was joined there by Rosie Jones (67), Becky Morgan (68) and Grace Park (68). Mi Hyun Kim ended one stroke further back at minus-12.
Rosales began her round at Eagle's Landing Country Club four strokes behind overnight leader Aree Song. Rosales got off to a good start with a birdie at the first and came back with a 20-foot birdie putt at the third to get to minus-9.
The 25-year-old then drained her fourth birdie in four rounds at the par-5 sixth. Rosales came right back to birdie the seventh after dropping a wedge within 1 foot of the cup.
Rosales posted three straight pars around the turn. She picked up her fifth birdie of the day at the par-3 11th from 10 feet out. Rosales then jumped into first place with back-to-back birdies from the 13th.
Rosales parred her final four holes to remain at minus-14 and one shot clear of the field, which gave her first tour title.
'It was tough watching them,' said Rosales, who finished some 45 minutes ahead of the final group. 'I tried so much not to watch and just keep my head somewhere else.'
Lee opened with back-to-back birdies before an eagle at the sixth to get to 10 under. She later birdied the eighth, but bogeyed the next hole. Around the turn, she birdied the 13th, 16th and 18th to grab a share of second place.
Jones sank a 4-footer at the second for birdie and made two birdies in a row from the sixth to move to minus-11. Jones then converted a 5-foot birdie at the ninth before chipping in for birdie at the next. She could only par in to share second.
'We weren't getting a lot of roll today, plus the wind was really gusty,' said Jones. 'It was coming at you and then turning around and going with you at some points.'
Morgan also started her round with a birdie on No. 2. She came back with a birdie at the eighth, but stumbled to a bogey at No. 10. Morgan erased that mistake by running off three straight birdies from the 11th before closing with five pars in a row.
'Well, I think at the beginning of the week, if you'd have told me that I would have a chance to win, I'd have been really happy,' said Morgan. 'I'd put myself in position a few times before.'
Park, the Kraft Nabisco Championship winner, birdied the second but stumbled to back-to-back bogeys from the third. She came back with three birdies over a four-hole stretch from the sixth. On the back side, she joined the crowd in second place with birdies at the 15th and 18th.
Song led by one stroke after grabbing the lead on her birthday Saturday. Sunday was much different for the 18-year-old. She carded a birdie at the fourth, but tripped to a bogey at the next. She later bogeyed the ninth to slide to minus-10.
She kept sliding from there too. Song double bogeyed the 13th and dropped another stroke at the very next hole. She capped her final round with another double bogey at No. 17 to finish in a tie for 23rd at 5-under-par 283.
Se Ri Pak, the 2003 winner, closed with a 2-under 70. She shared seventh place at 11 under par with Natalie Gulbis and Rachel Teske.
World No. 1 Annika Sorenstam closed with a 71 to end one stroke further back at minus-10. Sorenstam was joined there by Kate Golden, Lorena Ochoa and Michele Redman.