Preheat oven to 400°F and line a baking sheet with parchment paper.
Halve the spaghetti squash lengthwise, scoop out the seeds, and roast cut-side down for 40 minutes until the flesh is tender.
While the squash roasts, press the tofu with a heavy object for 15 minutes to remove excess water, then crumble it into small pieces with your hands.
Heat the olive oil in a large skillet over medium heat, then add the crumbled tofu, garlic powder, sea salt, and black pepper.
Sauté the tofu for 8-10 minutes, stirring occasionally, until it becomes slightly golden and firm.
Pour in the marinara sauce and dried oregano, then stir in the fresh baby spinach until it is just wilted.
Use a fork to scrape the squash flesh into noodle-like strands directly into the squash shells or a serving bowl.
Top the squash strands with the tofu marinara mixture and finish with a generous sprinkle of nutritional yeast.