Mix all ingredients well. Cover and refrigerate for at least a few hours (up to 2 days). Note: if using leftover mashed potatoes, do this the evening you make them fresh, and then refrigerate the mixture.
Preheat oven to 375°F Using a piping bag with a large decorative tip (or cut the tip from the bottom of a Ziploc bag), pipe approximately 1/4 cup each of the mixture onto a parchment lined baking sheet 1 inch apart.
Spray rosettes with non-stick cooking spray and sprinkle with a bit more paprika. Bake for 18-20 minutes or until heated through.