For the Pot Roast:
Sprinkle whole wheat flour and brown sugar across the bottom of a crockpot. Roll a 2.5 lb roast around in the flour and sugar. Mix together 1/2 c pumpkin, 1/2 c orange juice, and 1 c cranberry juice, then pour the mixture over the roast. Cook on high for 6 hours, then shred the roast.
For the Sandwich:
Toast a whole wheat bun. Put a handful of arugula on the bottom half of the bun. Cover with pot roast. Add some tomato slices and avocado. Add the top bun.