Cook pasta according to the package directions.

In a large skillet, heat olive oil. Cook the onions with salt and pepper for 6-8 minutes. Add the beef broth and roast beef.

When the noodles are cooked, drain and combine with the onions. Cook for 5-7 minutes.

In a medium saucepan, heat butter and add flour to thicken. Add milk, bring to boil. Add cheese, mix well. Once melted, pour over the noodles and onions. Add parsley and mix together. Pour into a 9x13 baking dish or lasagna pan.

Cover with aluminum foil and bake in a 350-degree oven for 10 minutes.