Steve Apparently orders Chinese food in the evening when he's on the roof just when snow starts falling, but since he did not have a cell phone with him or Chinese menu there's no way he could have called the restaurant and placed an order without getting off the roof.
Steve refuses to get off the roof until Laura goes out with him. But he would have to get off the roof to eat, go to the bathroom or go to school.
At approx. 14 mins. When Carl is coming downstairs and says, "Well, I'm off," the boom mic shadow can be seen moving across the set.