In a small bowl, combine the paprika, garlic powder, salt, and black pepper and stir to blend.
Spray the slow cooker insert with cooking spray. Trim any excess fat from the chicken thighs on a cutting board.
Sprinkle about half of the spice mixture over the tops of the chicken thighs and rub it in, then flip the thighs and sprinkle the remaining spice over the other side.
Roll each thigh if desired and place them in the slow cooker seam/rolled side down in a single layer or slightly overlapping.
Pour the BBQ sauce evenly over the chicken thighs, cover, and cook on low for 4 to 5 hours until the chicken reaches at least 165°F.
When cooked, preheat the oven broiler. Line a sheet pan with aluminum foil and lightly spray with cooking oil.
Arrange the thighs on the prepared sheet pan with space between each. Brush additional BBQ sauce over the tops.
Broil the thighs 1 to 3 minutes to caramelize and crisp the outside, watching closely to avoid burning, then remove and serve.