Preheat your oven to 375°F (190°C) and grease a muffin tin or line it with paper liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt until well combined.
In another bowl, mix the milk, melted butter, egg, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
Gently fold in the cooked sausage, cheddar cheese, and green onions if using.
Divide the batter evenly among the muffin cups, filling each about 2/3 full.
Bake for 15-18 minutes or until the tops are golden brown and a toothpick inserted into the center comes out clean.
Remove from the oven and brush the tops with melted butter for added flavor.
Allow the rolls to cool for a few minutes before serving.