Dissolve yeast in 1/4 cup of warm water in a small bowl; let stand for 5 minutes. Mixture should be foamy if your yeast is still good (and if it isn’t, toss it out and start over with fresh; if it helps at all, I did stir mine just a bit to get the foam to come).
In a large bowl, mix together 2 cups flour, pumpkin puree, milk, melted butter, sugar, salt, ginger, nutmeg, and cardamom. Stir in yeast mixture and continue stirring until evenly mixed. Turn dough out onto a floured surface.
Begin kneading. As you go, add the remaining 3/4 cup of flour, a bit at a time, until the dough is soft and elastic (it should feel a bit tacky, but shouldn’t stick to your hands).
Place the dough in a large bowl that has been lightly oiled, turning to coat the top. Cover and let rise in a warm, draft-free place for 45 minutes or until doubled in size.
Meanwhile, prepare the cinnamon filling by stirring together the softened butter, brown sugar, vanilla extract and cinnamon in a small bowl until smooth. Set aside.
Punch dough down; cover and let rest for 5 minutes. Roll the dough into a 12×10″ rectangle on a floured surface. Spread the cinnamon mixture in a thin layer over the dough, leaving a bit of a border at the edges.
Roll up the rectangle tightly, starting with a long edge, pressing firmly to get rid of any air pockets; pinch seam and ends to seal. Cut roll into 12 1-inch slices. Place slices in a lightly buttered 9×13″ rectangular pan. Cover with a clean towel and place in an unheated oven overnight.
In the morning:
Remove pan from the oven and remove the towel. Preheat oven to 375°F. Bake rolls for 20 minutes or until golden brown. Let cool for 15 minutes before drizzling with caramel icing.