Peel and dice sweet potatoes into even cubes, about 1/2-inch squares. Preheat oven to 400 degrees F.
In a large bowl, toss sweet potato cubes with oil, chili powder, paprika, salt, and pepper until evenly coated.
Pour potatoes onto a baking sheet lined with parchment paper or a silicone mat to avoid sticking. Roast for 30 to 40 minutes, stirring every 10 minutes until potatoes are fork-tender.
While potatoes are roasting, prepare the dressing. Whisk all ingredients in a small bowl and set aside.
Add kale and spinach mix to a large salad bowl along with roasted sweet potatoes, bacon, apple slices, and feta cheese.
Pour dressing over salad just before you're ready to eat. Serve immediately.
Notes
I cook the bacon while the sweet potatoes are roasting. You can bake it in the oven with the potatoes, or fry it in a skillet on your stovetop.