Place turkey breast on a sheet pan and dry with paper towels.
In a small bowl combine paprika, thyme, salt, pepper, garlic powder, and olive oil. Spread spice mixture evenly over both sides of the turkey breast.
Sprinkle garlic cloves, onions, and rosemary evenly over the bottom of a 6-quart sized slow cooker. Place the turkey breast inside.
Cover and cook on the Low setting for 3 hours. Cook until the turkey reaches an internal temperature of 165°F. Check at 2 ½ hours and continue to cook as needed.
Remove the turkey from the slow cooker and place on a sheet pan lined with foil.
Set oven to broil. Place the turkey inside about 12-inches away from the top. Broil until the skin is golden brown and crispy, 5 to 7 minutes. Keep a close eye that the skin does not burn. Allow to rest for 10 minutes before slicing. Meanwhile make the gravy.
Strain the contents of the slow cooker into a bowl, reserving only the juices. It should yield about ½ cup of liquid.
Heat a medium-sized pan over medium heat. Melt the butter in the pan and then whisk in the flour. Once a pale roux forms, turn the heat up to medium-high.
Gradually whisk in the reserved turkey juices and ½ cup of chicken stock. Continuously stir until thickened. Add more chicken stock as needed until the desired consistency is reached. Season gravy with salt and pepper. Slice the turkey and serve with gravy.