Add all of the ingredients, except garnish to the liner of your Instant Pot. Do not stir, but press the noodles down (if necessary) so they're submerged in liquid.
1 lb ground sausage, 4 cups water, 2 16 oz jars tomato basil soup, 1 13 oz jar pizza sauce, 1 4.5 oz jar sliced mushrooms, 1 medium tomato, 1/4 - 1/3 cup thinly sliced pepperoni, 1/2 tbsp dried rosemary, 1 tbsp minced garlic, 1/2 cup elbow pasta