Bring a large pot of lightly salted water to a boil. Cook risoni for 8 to 10 minutes, or until al dente; drain and rinse with cold water.
When risoni is cool, transfer to a medium bowl and mix in olives, feta cheese, parsley, dill and tomato. In a small bowl, whisk together oil and lemon juice. Pour over pasta and mix well. Season with salt and pepper to taste. Chill before serving.