Preheat an oven to 400 degrees F.
Add the onions, pumpkin, red chili flakes, olive oil to a large baking dish, and season with sea salt to taste; toss well to fully coat the ingredients. Roast the vegetables until the pumpkin is soft and golden, about 40 to 45 minutes.
Pour the honey and red wine vinegar into a small saucepan and bring to a boil. Reduce the heat and simmer for 5 minutes.
Transfer the pumpkin and onion to a serving dish and then drizzle with the honey dressing and mint leaves.