Melt butter in a medium sauce pan of medium heat. Add in flour and whisk together to make the roux. Add in garlic and stir for 20 seconds. Add in milk, heavy cream, sage, rosemary and stir for 3-4 minutes.
Add in pumpkin, cinnamon, salt, pepper and whisk until smooth. Add in cheese at the very end and serve warm.
(I also added nutmeg and red pepper chili flakes on mine but that is optional).
Use this sauce on spaghetti squash or regular pasta!