1. Preheat oven to 450°.
2. To prepare pork, heat a large skillet over medium heat. Add oil to pan; swirl to coat. Add onion and garlic; sauté 3 minutes. Add greens and next 3 ingredients (through raisins); cover and cook 4 minutes or until greens wilt, stirring occasionally. Uncover, and cook 3 minutes or until liquid evaporates.
3. Place greens mixture in a food processor; pulse 3 times or until chopped. Transfer mixture to a bowl. Add breadcrumbs, rosemary, and salt, tossing to combine.
4. Cut horizontally through center of pork, cutting to, but not through, other side using a sharp knife; open flat as you would a book. Place pork between 2 sheets of plastic wrap; pound to an even thickness using a meat mallet or small heavy skillet. Layer pancetta over pork. Spread dandelion stuffing over pork, leaving a 1/2-inch margin around outside edges. Roll up pork, jelly-roll fashion, starting with short side. Secure at 2-inch intervals with twine.
5. Place pork in a shallow pan coated with cooking spray. Bake at 450° for 15 minutes. Reduce oven temperature to 325°; bake 30 minutes or until a thermometer inserted in center registers 145°. Transfer pork to a platter, reserving drippings in pan. Cover pork with foil, and let stand 15 minutes.
6. To prepare sauce, stir broth, 1/4 cup muscadine wine, and white wine into pan drippings, scraping pan to loosen browned bits. Pour wine mixture into a small saucepan.
7. Combine cornstarch and 1 tablespoon water in a small bowl. Add cornstarch mixture to broth mixture; bring to a boil. Cook 1 minute, stirring constantly. Remove from heat; stir in butter.
8. Cut pork into 14 slices. Serve with sauce.