In 1993, Roiphe, then 24, rebuked college coeds protesting sexual violence. In her debut book, “The Morning After: Sex, Fear, and Feminism on Campus,” she groused, “Now instead of liberation and libido, the emphasis is on trauma and disease.” Like a sex advocate for smart girls, ages 18-25, she dismissed caution, sniffing: “It’s a difficult backdrop for conducting one’s youth.” Some were shocked by her cavalier concern: that focus on STDs and date rape might stymie erotic adventure. But her yen for passion remains the drumbeat for her writing.