The Scream 4 star, 22, was initially signed up alongside Selena Gomez and Vanessa Hudgens to shed their clean-cut images and play college students gone bad, but she ended up pulling out of the project - and Korine can understand why.
He tells the New York Post, "That was just - what do you call it? Creative differences. I make a specific type of film, and it goes hard. It's not always for everyone."
Ashley Benson was hired in Roberts' place and she is featured in the film getting drunk, puffing on cigarettes and engaging in a raunchy threesome with Hudgens and James Franco's drug dealer character, and Korine knows the edgy sex shoot wasn't easy for his young leading ladies.
He says, "I think at times it was overwhelming for them. But I thought that was part of the scene and that's how they should be feeling."
The intimate scenes even prompted former Disney star Hudgens to rule out taking part in any other sex shoots in the future - she previously said, "It was very nerve-racking for me. I told my agent that I never want to do it ever again."