Seth Rogen knows exactly what to do if faced with the apocalypse. “Heroin,” he told reporters at a party for his film “This Is the End” at the Jazz Room at the General. “That’s a good time to try something like that.” Director Evan Goldberg was more practical, saying, “A gun. You get whatever you want with a gun . . . You get food, travel companions, drugs and beautiful ladies.” Also at the the Fiji water and Svedka-sponsored bash were Bobby Cannavale and Rose Byrne, who sneaked in together.