'I didn't miss any greens,' said Rosales. 'I hit all the greens and missed only three fairways. I am happy the way it turned out.'
Lorena Ochoa posted a 68 to join Angela Stanford, Heather Bowie and Sung Ah Yim in a tie for second at 4-under par. Juli Inkster was one shot further back at 3-under-par 69.
Rosales, who earned her first career victory on the LPGA Tour last year at the Chick-Fil-A Charity Championship, started on the 10th tee of the Palmer Course at Turtle Bay Resort Golf Club and picked up her first birdie of the day at the par-5 12th. She then hit her tee shot inside 8 feet for a birdie at the par-3 13th and drained a 20-foot putt for a birdie at the par-3 15th.
The 26-year-old played her approach within 3 feet of the hole for a birdie at the par-4 16th and kept on cruising around the turn until she reached the par-5 third when Rosales chipped her third shot 8 feet from the hole and converted the putt for her fifth birdie of the day.
Rosales parred her next five holes before her third shot to the par-5 ninth landed within 10 feet of the cup. She then ran home the birdie try to finish two shots clear of the field.
'I felt like I was going to shoot low, but I didn't know it was going to be this low,' she said. 'I am just happy and hope that I can keep going until the end.'
Amateur sensation Michelle Wie is taking advantage of the LPGA Tour's stop in her native Hawaii and the 15-year-old had a rocky start with two birdies and two bogeys on the back side of the Palmer Course.
'I have to say I was a little bit nervous coming in because I had not played in a long time,' said Wie. 'Even after I made my birdie I still felt a little bit insecure.
Wie rolled in an 18-foot putt for a birdie at the par-3 fourth and tallied a birdie at the par-4 sixth for a round of 70.
'I think I left a lot behind,' said Wie. 'It was one of those rounds where I could have shot really low.'
Wie shared seventh place along with Cristie Kerr, Becky Morgan, Joellyn Crooks, Hee-Won Han, Grace Park, Rosie Jones, Carin Koch, Pat Hurst, Christina Kim, Lindsey Wright, Jimin Kang, Brittany Lincicome and Eva Dahllof.