In a small bowl, stir yeast into warm water; set aside to proof. (It’ll get very foamy in 5-10 minutes if your yeast is any good; if it’s not, hold off on this recipe!)
In a large bowl, whisk together flour, sugar, nutmeg and salt.
Add pumpkin puree and margarine to your foamy yeast mixture; blend well.
Make a well in your dry mix and add liquid, stirring to incorporate.
Knead for a couple of minutes until smooth, adding extra flour a little bit at a time as needed to keep it from sticking to everything. (Don’t add too much or your rolls will end up tough!) Gently poke the dough with your finger; if the indent bounces back, you’re good to go.
Cover tightly with plastic, set in a warm, draft-free place, and go write some letters to vegan political prisoners for an hour while your dough rises.
Once it’s about doubled, punch it down and roll out until it’s rectangular and about ¼-½” thick.
Slather with melted margarine and sprinkle brown sugar and cinnamon evenly over the top.
Applying slight pressure, roll the dough up like a jelly roll. If you want wide, squat buns with a ton of rings, roll it up the long way and make thinner slices; if you’d rather have more, taller buns (like the ones pictured), roll it up the short way and make thicker slices.
Firmly saw through the roll with a serrated knife to create 8 or so equal slices.
Arrange in a lightly-greased pan (9×13″ for squatter buns, else a 9″ cake pan); it’s okay for there to be a little bit of room between the rolls, as they’ll expand into each other and create that nice pull-away effect.
Cover and set in a warm place to rise for another 40 minutes.
Bake at 375° for 25 minutes.
While the buns bake, whisk together icing ingredients until smooth.
Set aside at room temperature (refrigeration will make it difficult to pour).
Drizzle icing generously onto warm buns and devour, with reckless abandon.