It seems that Greene's deal was never completed. This could be the result of Greene finally coming to an agreement with Summit over her pay in The Twilight Saga: Breaking Dawn. Though Scream 4 will begin production in Michigan next month, and the vamp flick isn't scheduled to kick off until later this year, there might be availability issues that affect the timing. Or, maybe fourth installments of horror franchises aren't her thing, even if they are reuniting Kevin Williamson with Wes Craven.
As for Roberts, this kicks off her first tastes of horror, and it's nice to see the actress go to the genre after making a name for herself elsewhere. While she's still that bubbly Nancy Drew, Roberts is really diversifying her roster these days, intermingling fluff with crime thrillers, drama, and now horror.
But she's just one of a whole cast, and since they're going for similar characters this time around, who would you like to see play the new Tatum, Randy, Dewey, and Gale? Or, do you like the other rumored/negotiating twists of Lake Bell, Hayden Panettiere, and Rory Culkin?