Bell peppers are sweet rather than spicy, and like onions, garlic, and celery, often help to round out dishes. This is why they're commonly used in dishes like shrimp fajitas, pepper steak, ...
I go the sheet-pan route in this recipe, roasting gnocchi alongside Italian sausages (you can use pork, poultry or plant-based) and sweet bell peppers to make a rich, savory one-pan meal.