Preheat the oven to 200 degrees. Peel the sweet potato and cut it into two-centimeter cubes. Slice the bell pepper into wide strips. Spread everything onto a baking sheet, drizzle with a tablespoon of olive oil, season with salt and pepper, and roast for twenty-five minutes until the edges caramelize.
Meanwhile, thinly slice the garlic and cut the red chili pepper into rings. Pat the prawns thoroughly dry, as wet shrimp will steam instead of sear.
Heat the remaining olive oil in a frying pan over medium heat and let the garlic and red chili gently infuse until the garlic turns light golden. Do not let it brown, as it will become bitter and overpower the dish.
Turn the heat up to high, add the prawns, and sear for two minutes per side until they just turn pink and firm. Remove the pan from the heat immediately; overcooked prawns become rubbery. Spoon the prawns along with all the garlic oil over the roasted vegetables, squeeze some lemon juice over top, and sprinkle with coarsely chopped parsley.