Preheat your oven to 400°F and line a large rimmed sheet pan with parchment paper for easy cleanup.
Drain the super firm tofu and pat it thoroughly dry with a clean kitchen towel before cutting it into 1-inch uniform cubes.
In a small mixing bowl, whisk together the gochujang, tamari, toasted sesame oil, garlic powder, and ginger powder until smooth.
Place the tofu cubes, broccoli florets, and sliced red bell peppers onto the prepared sheet pan.
Pour the spicy gochujang mixture over the tofu and vegetables, tossing with your hands or a spatula until every piece is well-coated.
Spread the ingredients out into a single layer, ensuring they are not crowded to allow for proper roasting and browning.
Roast in the center of the oven for 20 to 25 minutes, flipping the tofu and tossing the vegetables halfway through the cooking time.
Remove from the oven when the tofu is golden and the broccoli edges are slightly charred and crispy.
Garnish the dish with red pepper flakes and sesame seeds before serving hot.