Preheat oven to 450F/230C. Line two baking sheets with parchment paper.
Slice the sweet potatoes in half lengthwise and then cut into quarters. Slice each quarter into wedges, about 1/2 inch thick at the ends. Place in a large mixing bowl.
In a small bowl, mix together the oil, thyme, salt, garlic powder, onion powder, pepper and chili flakes. Pour over the wedges and toss to combine.
Arrange the sweet potatoes onto the baking sheets, ensuring there is adequate space between each, and they are not over-crowded. Bake in the oven for 20 minutes, then remove from heat and flip the potatoes to roast the other side, bake for an additional 15 minutes, or until crispy and golden.
Prepare the ranch dip: In a small bowl, combine the coconut yogurt, apple cider vinegar, dill, onion powder, sea salt, paprika and pepper. Mix to combine.
Transfer the sweet potatoes to a bowl and serve along with the ranch for dipping.