Preheat your oven to 425°F (220°C). This high heat will give the vegetables a nice golden color and enhance their flavors.
In a large mixing bowl, combine the cauliflower florets, sliced red bell pepper (or cherry tomatoes), cremini mushrooms, and green olives.
Drizzle the vegetables with 2 tablespoons of extra virgin olive oil. Add the freshly squeezed lemon juice, capers, kosher salt, and freshly ground black pepper. Toss everything together until the vegetables are evenly coated.
Spread the vegetable mixture evenly on a baking sheet. Make sure there's plenty of space between the pieces to ensure they roast rather than steam.
Roast in the oven for about 25-30 minutes, or until the cauliflower is tender and golden brown. Stir halfway through to ensure even roasting.
Once the vegetables are roasted to perfection, remove them from the oven and let them cool slightly. If desired, sprinkle with chopped parsley to add a fresh, vibrant touch before serving.