In the ever-fickle nightlife world, roofs are on fire. Rooftop fetes are the latest celeb party craze. In NYC, Enrique Iglesias and Michelle Branch dropped by the Tribeca Rooftop and ‘N Sync’s Joey Fatone mingled with the bunnies on Playboy’s terrace aerie. Leonardo DiCaprio and Tobey Maguire partied under the sky at L.A.’s Standard, while the open-air, glass-floored Ghost Bar at Las Vegas’ Palms hosted the MTV Real World cast. What’s with the alfresco skylarking? ”Celebrities like it because it’s an exclusive, elitist thing,” says Will Candis, rep for NYC’s Ava Penthouse Lounge, where Russell Simmons has alit. ”It limits the number of people at the party.” For the average person it’s the chance to be above it all. ”The [roof] lifestyle is open for the price of a cocktail.”