Cook the sausage in a large, deep-sided saute pan over medium-high heat until just browned, about 3 minutes. Add the broth and pumpkin. Whisk to combine, then bring to a simmer. Let cook 5 minutes. Stir in the half and half and 1 ounce cheese. Season to taste with crushed red pepper. Remove from heat and add the cooked pasta and arugula. Stir until arugula is wilted, about 1 minute.