Preheat the oven to 375° and gather one kind or mixed sweet potatoes.
Place the sweet potatoes in the wash bowl or salad spinner. Scrub the sweet potatoes really well with a scrub glove or vegetable brush. They brighten up after the scrub (so pretty).
Cut the sweet potatoes to size, 1 1/2 inch to 2 inch pieces or larger. If the pieces are too small they get overdone on the inside before the have picked up color on the outside.
Rinse the cut up sweet potato pieces in clean water in the wash bowl and drain, but not completely. They don’t need to be totally dry. A little water helps the dried spices to adhere to the sweet potatoes in the step next.
Place the rinsed sweet potato pieces in a large prep bowl. Sprinkle with dried spices of your choice. In this one I used 2 tsps ground cumin, 2 tsps ground coriander, 1 tsp Aleppo (sweet and piquante hot red pepper flakes), and a few grinds of black pepper. Tossing the potatoes in the bowl gives the best distribution of spices (and kinda fun), but stirring with a wooden spoon or flat spatula will work well too.
Set aside the sweet potatoes with the spices for 10 minutes to 20 minutes. This time allows the spice to absorb moisture and not burn during the roasting. It also flavors the sweet potatoes nicely.
On a parchment paper lined bake sheet, place the spiced sweet potatoes on a single layer and put in the oven for 20–30 minutes (check at 20 minutes). The potato side on the paper should be brown in spots. When the undersides are browned in spots, turn them over and roast for another 10–15 minutes.
Take the sweet potatoes out when they are done all the way through. You can toss them in a dressing if you like or serve them as is.