Preheat the oven to 425˚F. Line multiple baking sheets with aluminum foil.
Place the sweet potatoes and red onion onto the same baking sheet. Add about 1 1/2-2 tbsp of olive oil, 3/4 tsp kosher salt, and 1/2 tsp of black pepper to the pan. Mix the sweet potatoes and red onion with the oil and seasonings until they are evenly coated. Roast them in the oven for about 20-25 minutes or until the sweet potatoes are fork tender and the red onions have slightly caramelized.
Add the sliced mushrooms to a separate baking sheet. Toss the mushrooms together with about 1 tbsp of oil, 1/2 tsp kosher salt, and 1/4 tsp of black pepper. Roast them in the oven for about 20-25 minutes or until all of the moisture from the pan has evaporated.
Add the broccoli florets to a separate baking sheet and toss them together with about 1 1/2 tbsp of olive oil, 1/2 tsp kosher salt, and 1/4 tsp black pepper. Roast them in the oven for about 15 minutes or until the broccoli is fork tender.
Heat a pan over medium high heat. Pat the halloumi slices dry with paper towels. Lightly brush both sides of the slices with olive oil. When the pan is hot, add the halloumi to the pan and cook until it develops a golden brown outer crust, about 2-3 minutes. Flip the halloumi onto the other side and cook for another 2-3 minutes.
To serve, portion the rice, sweet potatoes, onions, mushrooms, broccoli, and halloumi between the serving bowls. Top each bowl with drizzle of the basil vinaigrette and enjoy!