Preheat the oven to 425 ̊. Peel the sweet potatoes and cut into a half-inch to one-inch dice. Toss with a generous amount of olive oil and salt and pepper to taste. Spread out on a rimmed baking sheet and roast until the sweet potatoes are beginning to brown and are tender and sweet on the inside. You may want to flip and move them around on the baking sheet once or twice during the roasting. This can take anywhere from 15 – 30 minutes, depending on the size that you cut the sweet potatoes.
While the sweet potatoes are roasting, put the amount of sour cream you would like to have for topping/dipping in a separate bowl. Add a few spoonfuls of tomatillo salsa and mix until combined. Taste, and add more salsa until it tastes good to you.
When the sweet potatoes are ready, transfer to a plate and drizzle with the tomatillo sour cream – or reserve the sauce on the side as a dip.