Preheat the oven to 375°F. Cut the cauliflower into florets. Place the cauliflower on a rimmed baking sheet, and drizzle with the olive oil. Toss well, then sprinkle with salt and pepper. Roast for about 25 minutes, until crisp-tender and browned at the edges.
Meanwhile, if you are using the sesame seeds, heat a dry skillet over medium heat. Add the sesame seeds and stir frequently for about 1 or 2 minutes, until they start to become golden. Transfer them to a plate.
In a small bowl, combine the soy sauce, sesame oil, honey, and Sriracha sauce. When the cauliflower is roasted, transfer it to a serving platter and drizzle over the sauce, or pass it on the size for everyone to drizzle over their portion. Sprinkle the top with sesame seeds, if desired, and serve hot or warm.