Cook pasta according to package directions. Drain and set aside.
In a large skillet, melt butter over medium heat. Stir in flour and cook for 1 minute.
Gradually whisk in milk and ranch seasoning. Cook, stirring, until thickened (2–4 minutes).
Stir in shredded cheddar until melted and smooth.
Add cooked pasta, chicken, and half of the bacon to the sauce. Toss to combine and heat through.
Season with salt and pepper as needed.
Serve topped with remaining bacon and fresh parsley if desired.