Rojas, the two-time defending champion, produced the sixth furthest jump of all time with her winning 15.47 metres.
Jamaica's Shanieka Ricketts took silver with a distant 14.89m and American Tori Franklin claimed bronze (14.72).
Rojas had opened with what is for her a conservative 14.60m.
After asome adjustments, she made no mistake on her second attempt, the world record holder sailing out to 15.47.
Thereafter came a 15.24, two fouls and a 15.39, with a comprehensive victory already in the bag.