In the bowl of a stand mixer, stir together 1 1/2 cups flour and yeast, set aside.
In a medium saucepan, whisk together pumpkin, milk, sugar, salt, and two tablespoons butter.
Heat on medium low heat, being careful not to boil, until very warm (about 120-130 degrees) - the butter will be almost melted and should be very hot, but not burning, to the touch.
Pour pumpkin mixture along with the beaten egg over the flour in the stand mixer fitted with a dough hook.
Mix on medium speed until mixture is wet.
Gradually add remaining 1 3/4 cup flour while mixer is on medium speed.
Add an additional 1/4 cup flour if needed, the dough should be pulling away from the sides and the bowl should be almost clean.
Keep the mixer on medium speed and knead for 8 minutes.
Turn dough out into a greased bowl, cover, and let rise for one hour or until doubled.
Punch dough down and roll out onto a floured surface into a large rectangle, about 12 x 10 inches.
Melt remaining 2 tablespoons butter and spread over dough, sprinkle with brown sugar and cinnamon.
Roll up starting with the long side as tightly as possible and slice into 12 slices.
Place slices cut side down in a 9 x 13 baking pan and allow to rise 30 minutes, covered.
Bake at 375 for 20 minutes, cool completely. For frosting, melt butter over medium low heat.
Stir in brown sugar, milk, vanilla, and salt.
Continue to cook 3 minutes.
Remove from heat and whisk in confectioner's sugar. Drizzle over rolls.