The 24-year-old Roberto grabbed a one-shot lead over Lucy Landicho despite a sputtering finish that saw her make a double-bogey on the 14th and close with two bogeys when the winds blew hard in the early afternoon.
Landicho made the most of the benign morning conditions with a 75 to put herself in the championship hunt in this event organized by the Women’s Golf Association of the Philippines.
Francis Bondad of Australia loomed as a potential foreign threat, carding a 77 to be in solo third.
The fancied Carmelette Villaroman, aiming to reclaim the title she last won in 1993, struggled all day, scoring a 78 to stay four shots off like Eva Miñoza and Anna Yu of Hong Kong with jungolfers Remijin Camping (79), Jayvie Agojo (80) and Geleen Handog (80) close on their heels.
Roberto said she had bad break with that double-bogey on 14th where her tee-shot landed on a difficult lie in the right bunker. She barely got out and chipped far past the flag.
"I was playing well, recovering some shots from outside the green and then you get a double without penalty. It was a bad break for me," said Roberto, who played with Villaroman in The Spirit International in Houston, Texas last year.
She actually birdied the par-5 15th from six feet to stay at one over and kept that score with another regulation par on the 16th.
She then bogeyed the par-4 17th.
Villaroman birdied the third but struggled the rest of the way with six bogeys and a double-bogey on the 15th. Handog could have been much closer if not for her own last-hole double.
Tournament sponsors are Pagcor, PCSO, the First Gentleman Foundation, Golden Donuts, Rep. Gilberto Duavit, Equitable-PCI Bank, Inquirer Golf Monthly, ICTSI, Slazenger, Nike Park and Crucible Gallery.