Beat egg and water in small bowl with fork or whisk, set aside.
Unfold pastry sheet on lightly floured surface. Roll pastry sheet into 16" x 12" rectangle, short side facing you.
Spread thin layer of sauce on pastry. Layer salami and basil on bottom half of pastry to within 1" of edge. Sprinkle with cheese, oregano and onions.
Starting at short side, roll up like jellyroll. Place seam-side down onto baking sheet, tuck ends under to seal. Brush entire pizza puff with egg mixture.
Bake 25 minutes or until crust is golden brown. Remove from baking sheet, let cool on wire rack (about 10 minutes).
Notes
Is there anything you can't make with a puff pastry?