Unfold pastry sheet onto a floured surface; press out folds. Layer half of salami on pastry, leaving a 1/2-inch border at the top. Top salami with 3 slices Swiss cheese.
Brush top edge lightly with water. Starting at the bottom, roll up pastry, pressing border at the top to seal. Repeat with remaining pastry, salami, and cheese.
Cut 1/2-inch-thick slices, and place on a greased, foil-lined baking sheet.
Bake at 400° for 12 minutes or until golden brown. Serve with Dijon or whole-grain mustard.