Preheat the convection oven to 400°F (204°C). Line a heavy-gauge rimmed baking sheet with parchment paper or a silicone baking mat to prevent sugar adhesion.
In a large stainless steel mixing bowl, whisk together the maple syrup, sriracha, olive oil, soy sauce, garlic powder, salt, and black pepper until a homogenous emulsion is formed.
Introduce the cauliflower florets into the bowl. Use a silicone spatula to fold the florets through the glaze until every surface is thoroughly and evenly coated.
Transfer the glazed cauliflower to the prepared baking sheet. Arrange in a single layer, ensuring at least 0.5 inches of space between florets to allow for proper steam escape and optimal browning.
Roast for 15 minutes. Remove the sheet from the oven and use a spatula to toss and rotate the florets to ensure even heat distribution.
Return to the oven and roast for an additional 10 to 12 minutes, or until the cauliflower is tender and the exterior edges exhibit significant dark caramelization and char.
Remove from the oven and allow to rest for 2 minutes on the sheet pan to let the glaze set. Transfer to a serving vessel and garnish with sliced scallions.