1. Preheat the oven to 325 degrees Fahrenheit.
2. Then proceed to butter the turkey breast on all sides, including the hollow of the breast. You should also season the breast meat with salt and pepper to taste.
3. You should place the turkey breast-side up in the roasting pan after arranging the vegetables on the bottom of the pan
4. Roast for 2 to 2½ hours in the oven (hen the meat hits 160 F, remove it from the oven).
5. While the turkey rests, transfer it to a cutting board and cover it loosely with foil for 30 minutes.
6. In the meantime, drain any drippings from the pan into a small bowl. You can combine some of the pan juices with the broth in another bowl
7. Proceed to place the roasting pan on a stove over medium-high heat and add some of the juice.
8. Make sure you scrape off any browned bits from the bottom of the pan. Add some flour and proceed to cook, stirring regularly, for 2 minutes.
9. Continue to whisk in the broth while continuing to swirl. You can bring it to a boil and cook for 3 minutes until the sauce has thickened.
10. Remove the veggies from the gravy and season with salt and pepper to taste.
11. Carve the breast and place it on a plate with the gravy.

You can watch this video recipe to know how well to cook an 8 lb turkey breast in the oven.