Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
Slice the spaghetti squash in half lengthwise and remove the seeds with a spoon.
Place the squash halves cut-side down on the baking sheet and roast for 40 to 45 minutes until the skin is easily pierced with a fork.
While the squash roasts, whisk the whole eggs, egg whites, grated Pecorino Romano, and Parmesan together in a bowl until combined.
Sauté the diced guanciale in a large skillet over medium heat until the fat has rendered and the meat is crispy.
Remove the skillet from the heat source and set aside briefly.
Once the squash is cooked, use a fork to scrape the flesh into long spaghetti-like strands.
Add the squash strands to the skillet with the guanciale and toss to coat in the rendered fat.
Quickly pour the egg and cheese mixture over the warm squash strands, tossing constantly and vigorously to create a creamy emulsion using the residual heat.
Season with salt and extra black pepper, and serve immediately to maintain the sauce texture.