Preheat oven to 450°F.
Marinate tofu in soy sauce in a small bowl for 10 minutes.
Toss broccoli with 2 tsp oil, ½ tsp salt and ¼ tsp pepper in another bowl.
Toss squash with remaining 2 tsp oil, ½ tsp salt, remaining ¼ tsp pepper and garlic on a large sheet pan (at least 12- X 16-in); bake 15 minutes. Remove pan from oven and stir; move squash to one side of pan.
Spread broccoli out on other side of pan; nestle tofu down center of pan, making sure each piece makes contact with pan. Return to oven; cook until squash is tender, 20-25 minutes.
Meanwhile, combine tahini, yogurt, lemon juice, water, remaining ¼ tsp salt, and sriracha to taste in a small bowl.
Plate tofu and vegetables; drizzle with tahini sauce and sprinkle with pepitas.