1 to 3 minutes. The heating time of Rosen bento microwave oven is 1-3 minutes, and then gradually increase the heating time to reach the appropriate temperature according to the different types and weights of bento. The heating time is also influenced by microwave oven power, food size and personal taste. Rosen is a franchise convenience store chain with branches in Kansai, China, Shanghai, Nanjing, Chongqing, Shenyang, Dalian, Hangzhou, Beijing, Wuhan, Changsha, Hainan, Tangshan and Baoding.