Cronenberg didn't cast Rob because of his tremendous Twilight Saga fame. In fact, he says, it made shooting a little more difficult...
"Actually the fame was a detriment," Cronenberg told us. "I mean, it's good for financing - but it's not necessarily good when you're on the street and there are a lot of Twihards around. But I think people will be really surprised, I mean, I think he's a terrific actor and that's why I went after him."
Source | Robsessed