Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Stir in the risoni and return to a boil. Cook the pasta uncovered, stirring occasionally, until cooked through but still firm to the bite, about 10 minutes. Drain well and let cool.
Mix the mozzarella cheese cubes, tomatoes, basil, chilli flakes and salt with olive oil in a salad bowl. Gently mix in the risoni pasta and toss lightly to coat the ingredients with oil.