In a glass measuring cup, combine the yeast, water, and 1 teaspoon of sugar; set aside to foam for about 5 minutes. In the bowl of an electric mixer fitted with the paddle attachment, combine the mashed sweet potato, 1/3 cup of sugar, greek yogurt, milk, melted butter, egg, pumpkin pie spice, and salt.
Switch to the dough hook, and add the yeast mixture and 3 cups of the flour. Mix the dough on low and allow it to knead for about 6-7 minutes. If dough is still too soft, add more flour, 1 Tablespoon at a time, until dough just cleans the bowl, but is very soft. It should still stick to the bottom of the bowl.
Coat a large bowl with cooking spray and place dough in bowl. Seal tightly with plastic wrap. Place bowl in a warm place and allow dough to rise until doubled in size, about 2 hours.
After dough has doubled in size, punch it down. Turn dough out onto a floured Silpat or floured countertop. With a rolling pin, roll it out to an 17x12-inch rectangle.
With a butterknife (or your fingers), spread butter evenly over the entire surface of the dough. Sprinkle the brown sugar over it, followed by the cinnamon.
In a mixing bowl, combine the raspberries, granulated sugar, and cornstarch. Sprinkle raspberry mixture evenly over the dough. Lightly pat it down with your fingertips to help the sugar and raspberries adhere to the dough. Roll dough tightly into a log (from long side to long side), ending with the seam side down. Pinch the ends to seal.
Using plain, unwaxed dental floss (or a sharp knife), slice the rolls into 12 evenly-sized rolls. Arrange the rolls cut-side down in the baking dish. Cover tightly with plastic wrap--make sure to coat plastic wrap with cooking spray so that it doesn't stick to the rolls as they rise.