Place soybeans, vegetable oil, tamari, and ketchup in a food processor and blend until just slightly textured (or mash by hand).
Open puff pastry sheet and lay flat. Cut along folds to make three pieces. Cut each of these crosswise, in half. On a lightly floured surface, roll out pastry to make six 5 x 7-inch rectangles.
Divide soybean filling among the six sheets (about ⅓ cup each). Spread over pastry, leaving ½-inch border around all edges. Lay one slice of Swiss cheese over filling. Moisten edges of the pastry with water. Roll up into a jellyroll shape, starting with the 5-inch edge. Pinch seams and edges to seal.
Wrap each roll separately with waxed paper or plastic wrap. Chill for at least 2 hours until firm.
Preheat oven to 425ᵒ F. Remove from refrigerator, take off coverings, and slice each roll crosswise into six equal rounds. Place on greased baking sheets, arranging end pieces seam-side down. Bake for 7 to 10 minutes. Serve hot or at room temperature.