Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a large bowl, toss cauliflower florets with cornstarch, salt, pepper, and a drizzle of neutral oil.
Spread the florets evenly on the baking sheet and roast for 25–30 minutes, flipping halfway through, until golden and crispy.
While the cauliflower roasts, combine soy sauce, maple syrup, vinegar, ginger, and garlic in a saucepan over medium heat.
Bring to a gentle boil. Stir in the cornstarch slurry and cook until the sauce thickens to a sticky consistency, about 2–3 minutes.
Once the cauliflower is done, toss it in the warm sauce until fully coated.
Sprinkle with sesame seeds and chopped green onions before serving. Serve hot.