Place habanero pepper, mango, and onion on a baking sheet. Drizzle with olive oil; toss to coat evenly.
Roast on the middle rack of the preheated oven for 10 minutes. Turn on the oven's broiler and roast for 5 more minutes. Move baking pan to the oven's top shelf; broil until onion and mango begin to brown and habanero pepper blisters, about 3 more minutes. Remove and slightly cool.
Wearing gloves, remove stem from habanero pepper and place pepper in a small food processor or blender; add mango, onion, garlic, cilantro, lime juice, and salt. Season with black pepper and cumin. Pulse until salsa is combined and slightly chunky. Refrigerate for 2 hours before serving for flavors to blend.