Heat oven to 350°F. Spray cookie sheet with cooking spray.
If using crescent rolls: Unroll dough; separate dough into 4 rectangles. Firmly press perforations to seal. If using dough sheet: Unroll dough and cut into 4 rectangles.
In small bowl, mix cream cheese and taco seasoning mix. Stir in Cheddar cheese, corn and onions. Spread 2 tablespoons cream cheese mixture over each rectangle to within 1/4 inch of edges.
Starting with one short side, roll up each rectangle; press edge to seal. With serrated knife, cut each roll into 6 slices; place cut side down on cookie sheet.
Bake 13 to 17 minutes or until edges are golden brown. Serve warm with salsa.