Preheat oven to 350°F (175°C).

Cook penne pasta according to package directions.

While pasta cooks, brown Italian sausage in a skillet over medium heat.

Drain excess grease from the sausage.

In a separate saucepan, melt butter over medium heat.

Add flour to the melted butter and stir continuously until light golden brown, ensuring not to burn.

Whisk in milk, garlic powder, salt, and pepper.

Continue whisking until the sauce thickens and is smooth.

Combine the sausage and sauce together.

Mix the sausage sauce with the cooked penne pasta.

Pour the pasta mixture into a casserole dish that has been sprayed with cooking spray.

Sprinkle shredded Italian cheese evenly over the top.

Bake in the preheated oven for 30 minutes, or until hot, bubbly, and golden brown.

Let stand for 10-15 minutes before serving.

Serve hot with garlic bread.