In the bowl of a stand mixer, proof yeast by combining 1/4 cup warm water (around 95F-110F) and 1/2 tsp sugar. Sprinkle yeast on top and allow to bloom for 5-10 minutes until frothy. If yeast does not foam, yeast is dead and will not rise- start over.
On low speed mix in half& half, sugar, pumpkin puree, melted butter, and egg.
In a separate bowl, whisk together flour, pumpkin spice, and salt. Add dry ingredients to wet, 1 cup at time.
Using a dough hook, set your mixer to low and allow it to knead 8-10 minutes. If you don't have a stand mixer, do this by hand.
Transfer dough to a lightly oiled bowl. Cover with plaster wrap and allow to rise in a warm place for 1 hour.
Transfer dough to a well floured surface & roll out in to a 14X16 rectangle. Spread softened filling butter across dough. Mix filling spices- brown sugar, pumpkin pie spice, and cinnamon. Sprinkle over buttered dough and use a spatula to spread evenly.
Starting from the short side, roll dough into a tight log. Cut an inch off of both ends & cut the rest into 12 even pieces.
Place cinnamon rolls in a parchment lined baking pan. Cover with plastic wrap and leave out to rise for 30 minutes.
Preheat oven to 375. Bake rolls for 20-25 minutes until golden brown. Allow to cool on a wire rack for 10 minutes before frosting.