Rosales, coming off a breakthrough win last week in Georgia, followed up a two-under 69 with a 67 but fell five shots behind new leader Kim Williams who shot a tournament-record eight-under 63 for a two-day haul of 131.
Fil-Am Dorothy Delasin tumbled from joint second to a share of 55th place as she failed to sustain the momentum of her opening-round 66, limping home with a 78 in the second round.
Suddenly, Delasin was 13 strokes off the pace.
Rosales, however, kept the Philippine flag waiving in the tourney on another stirring round she embellished with five straight birdies from No. 3.
She actually started with the wrong foot with a bogey on the par-4 No. 1 but quickly made up for it and was already four-under as she made a birdie on No. 7 which she eagled on Thursday.
"Right now, I feel really good. I feel really confident and I will just take that every week and put myself in a good position again and get that second win," said Rosales, who won her first career title Sunday at the Chick-fil-A Charity Championship. — With reports from AFP