For the vegetables: Place an oven rack in the center of the oven and preheat to 375 degrees F. Coat a large rimmed baking sheet with vegetable oil spray. Combine all the vegetables in a large bowl. Drizzle with the olive oil and sprinkle with rosemary, salt and pepper. Toss to coat. Spread out the vegetables in a single layer on the prepared sheet. Roast until tender, 25 to 30 minutes.
Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until tender but still firm to the bite, stirring occasionally, 8 to 10 minutes. Drain and place in a large serving bowl.
For the dressing: In a medium bowl, whisk together the buttermilk, safflower oil, sour cream, lemon zest, lemon juice, chives, mint, parsley, salt and pepper until smooth.
Add the roasted vegetables and dressing to the cooked pasta. Toss until all ingredients are coated and serve.