Remove cereal mixture from pan; place on cutting board. Cut crosswise in half. Arrange single row of half the remaining marshmallows lengthwise down centre of each rectangle; fold both long sides of each rectangle to centre of rectangle then press to form log. Tap any remaining graham crumbs from pan onto cutting board. Roll logs, 1 at a time, in crumbs. Cut each log into 8 slices to resemble sushi.