Bring a large pot of lightly salted water to a boil. Place tortellini in the pot, and cook for 7 to 8 minutes, until al dente. Drain, and cool.
In a large bowl, mix the cooked tortellini, red bell pepper, broccoli, carrots, olives, and garlic.
In a separate bowl, stir together the mayonnaise, pesto, milk, Parmesan cheese, olive oil, and vinegar. Pour over the tortellini and vegetables, and gently toss to coat. Cover, and place in the refrigerator 1 hour, until chilled. Serve over spinach leaves.