Preheat broiler. Place squash and 2 tablespoons water in a large microwave safe bowl; cover with vented plastic wrap. Microcook on 100 percent power (high) for 5 to 8 minutes, until crisp tender, stirring once.
Transfer squash along with cauliflower to a 15x10x1-inch baking pan. Sprinkle with salt and pepper then lightly coat with cooking spray. Broil 4 to 5 inches from heat for 10 to 12 minutes, until tender and beginning to brown, stirring once halfway through broiling time.
Meanwhile, prepare couscous according to package directions; set aside. In a small microwave-safe bowl combine the butter and chili sauce. Briefly microcook on high just until butter is melted.
Divide couscous among 4 shallow bowls. Top with vegetables, pistachios, chili-butter, and thyme.