Heat up your grill or preheat oven to medium/high broil.
Place your chopped sweet potato and potatoes in a large pot and cover with water. Bring to a boil and cook or "parboil" for about 10 minutes or until almost tender. You want them to be semi-tender - firm enough to stay on a skewer, but tender enough that they won't require too much time on the grill/in the oven. Drain and let cool slightly.
Assemble skewers by adding the vegetables in layers to the skewers, leaving enough room at the top and the bottom to help with flipping and preventing vegetables from falling off. Brush with a neutral, high-heat oil such as avocado or coconut oil (or sub water if avoiding oil) and sprinkle generously with salt and pepper on all sides.
Grill (or broil) until grill marks are present and vegetables are tender and cooked through - about 10-15 minutes. Flip once at the halfway mark to ensure even cooking. If browning too quickly, move to the perimeter of the grill, where the heat is less intense (or turn oven heat down/move the pan lower in the oven). If grilling corn, place directly on the grill without the husk, or on the broil pan with the other vegetables.
While the vegetables are grilling, prepare your chimichurri or BBQ sauce (optional).
Enjoy as is or with my Chimichurri Sauce or BBQ sauce! Best when fresh, though leftover grilled vegetables will keep covered in the refrigerator up to a few days. Reheat on the stovetop in a cast-iron or metal skillet or in the oven at 350 degrees F (176 C).