Toss cauliflower florets with olive oil. Spread in single layer on baking sheet.
Roast at 400°F for 15-20 minutes until browned and tender.
In a small bowl, whisk together gochujang, soy sauce, maple syrup, rice vinegar, sesame oil, garlic, ginger, and cornstarch.
Pour sauce over roasted cauliflower and toss to coat.
Roast 10-15 minutes more until sauce thickens.
Season with salt and pepper to taste.
Serve over rice garnished with sesame seeds and scallions.