So there must be a clear and non-hostile way like Peg said. Maybe you say something like, "I feel horrible for what you are going through and want you to know you're welcome here through the 1st. But I need my room back. Do you need me to help you guys get setup somewhere else in the house?"

And if that doesn't work.... Scream! Jk but not really lol. Healthy boundaries, much easier said than done.