Heat the oven to 400°F. Line a large rimmed baking sheet with parchment paper.
Put the sweet potatoes on one side of the baking sheet. Toss them with the olive oil and a pinch of the listed salt and pepper, then spread them in a single layer.
In a large bowl, combine the ground turkey, egg, breadcrumbs, diced onion, garlic powder, and the remaining salt and pepper. Add ¼ cup of the barbecue sauce and mix gently until combined.
Shape the turkey mixture into a compact loaf on the empty side of the baking sheet. Leave a little space between the loaf and the potatoes so they roast evenly.
Bake for 25 minutes. Brush the remaining ¼ cup barbecue sauce over the top of the meatloaf.
Return the pan to the oven and bake for about 15 to 20 minutes, until the meatloaf reaches 165°F in the center and the sweet potatoes are tender. Let the meatloaf rest for 5 minutes before slicing.