In sibling directors Bill and Turner Ross ’ latest, “Gasoline Rainbow,” five Oregon teens just out of high school make their meandering way some 500 miles to reach the coast for what’s been billed as the “End of the World” party. HT Image They are like countless young protagonists before them: on the road to find out. But while they share much of the same yearnings and anxieties of American road travelers from “On the Road” to “Easy Rider,” the circumstances of their particular coming of age are uniquely theirs — and what’s on the radio dial is, too. “Dude, I want to listen to some Shakira, bro,” one says from the backseat of their van. Unlock exclusive access to the latest news on India’s general elections, only on the HT App. Download Now! Download Now! This being the Ross brothers — the makers of the Texas-Mexico border portrait “Western” and “Bloody Nose, Empty Pockets,” in which they brought 22 people to a Las Vegas dive bar and asked them to act as though it …