Preheat the oven to 425 degrees F. Place the cauliflower on a rimmed baking sheet. Toss with 2 tablespoons olive oil and sprinkle with some salt and pepper. Roast until tender and charred in places, about 20 minutes. Let cool.
In a large bowl, combine the roasted cauliflower, cherry tomatoes, chard leaves and stems, lentils, orzo, olives, parsley, dill and mint. Add the lemon zest and juice, red pepper flakes, the remaining 2 tablespoons olive oil and salt and pepper to taste. Fold to combine and serve.