Preheat the oven to 375°. In a large saucepan, melt the butter over medium-high heat. Add the onion and bell pepper and cook, stirring occasionally, until soft, about 7 minutes; remove from the heat. Stir in the cream cheese, 1/2 cup pecorino-romano, the paprika and mustard. Stir in the artichoke hearts and shrimp; season with salt and pepper.