Preheat oven to 375 degrees. Brush spaghetti squash halves with olive oil and season with salt and black pepper.
Place cut-side down on a nonstick baking sheet (alternately, line with nonstick aluminum foil or parchment paper).
Roast for 30-40 minutes or until tender and a knife can be easily inserted into the squash. Let cool.
Shred the pulp into a large bowl.
Add panko, Parmesan cheese, eggs, ranch salad dressing, garlic powder, onion powder and 2 teaspoons salt and 1 teaspoon freshly ground black pepper. Mix well.
Working with 1 cup at a time, press the mixture into a rectangle to approximately 1/2-inch thickness.
Cut into "fries."
Place on a parchment-paper lined baking sheet. (At this point, you can refrigerate uncovered up to 24 hours to bake later.)
Bake fries at 375 degrees for 30-40 minutes, turning once.
Serve with ketchup or marinara sauce.