Prepare: Preheat the oven to 425 F and line two large baking sheets that will fit on one oven rack at the same time with parchment paper.
Slice and Season Squash: Slice into the squash with a sharp knife, cutting lengthwise from the middle to one end, then from the middle to the opposite end until you can break it in half. Remove the seeds and pulp. Season the cut sides with salt and pepper.
Bake Squash: Place the squash halves cut-side down on one half of one of the baking sheets and add to the oven.
Roast Tofu: Cut the tofu into cubes and toss with the cornstarch, soy sauce or tamari, sesame oil, garlic powder and some black pepper in a bowl until all the pieces are coated. After the squash has been in the oven for 10 minutes, add the tofu pieces to the other half other baking sheet.
Roast Vegetables: Add all of the chopped vegetables to the other baking sheet and toss with 1 tbsp olive oil, salt and pepper. Add to the oven as well. The squash should roast about 35-40 minutes in total, while the tofu and veggies should roast about 25-30 minutes.
Mix Sauce: Add all of the sauce ingredients to a small bowl and whisk together until smooth.
Create Squash Noodles: Once you can pierce the squash skin with a knife, remove everything from the oven. Pull a fork through the spaghetti squash flesh to create strands, or "noodles", until you've scraped all the flesh away from the skin.
Serve: Divide the squash between 4 servings and top each with equal amounts of tofu and vegetables. Drizzle each with desired amount of sauce, you may use it all or have some extra. Serve topped with green onions, fresh cilantro and sesame seeds.