Place pork roast in self-sealing plastic bag. Combine parsley, onion and garlic in food processor; pulse until minced. Add remaining ingredients and process to blend.
Reserve 1/4 cup chimichurri sauce; set aside. Coat pork in plastic bag with remaining mixture. Seal bag and refrigerate overnight.
Heat oven to 375 degrees F. Remove pork from marinade and place on rack in shallow pan (discard any leftover marinade). Roast 30 to 35 minutes per pound until internal temperature reaches 150 degrees F. Let stand 10 minutes before slicing.
Serve sliced loin filet with reserved chimichurri sauce.