Prep Work: Combine all ingredients through chicken and marinate covered in refrigerator. Chop potatoes and chop onions; store together.
In a marinating dish combine all ingredients up to and including chicken. Cover and marinate up to 24 hours in refrigerator. If making day of, try to marinate for a few hours, or at least 15 min..
Preheat oven to 450 degrees. Grease two rimmed baking sheets or pans. Boil spaghetti according to package instructions; rinse and return to pot when done.
Lift chicken out of dish and spread out on one of the baking sheets. Place vegetables on the second sheet and pour any remaining marinade from chicken over them; toss to coat and add as much olive oil as needed to lightly coat. Salt and pepper.
Roast both trays 10 min., then stir chicken and vegetables and roast 5-7 more minutes. Cut one chicken chunk open and take out if no longer pink. Remove finished chicken from oven, cover with tinfoil tent for 10 min., then place in covered serving bowl.
Roast vegetables until onions are soft and carmel colored (stirring once or twice), 15-17 min or until all are soft and beginning to brown. Sprinkle lightly with black pepper and more salt if needed to bring out flavor.
Toss all together in serving dish or spaghetti pot if large enough: vegetables, chicken, noodles and just enough spaghetti sauce for your taste. Sprinkle individual servings with parmesan or cheddar cheese if desired.
