1. Cook tortellini according to package directions.
2. Drain and rinse with cold water. Set aside to cool.
3. Combine oil & vinegar dressing and pesto in a small jar with tight fitting lid.
4. Shake well to combine. Set aside.
5. Combine tortellini, cheese, olives, peppers and tomatoes (if using) in a large glass bowl.
6. Stir to combine.
7. Shake dressing & pesto to combine. Pour over pasta salad.
8. Mix well.
9. Cover and refridgerate at least 1 hour.
10. Serve cold.