Everything Under the Moon

Hello! I'm away from my room for the summer, and my roommate is there with her not so trustworthy friends. Does anyone have any spell recommendations for protection of my room? Thank you!

Bundles of sage or rosemary (or both, I suppose) hung above a doorway is said to protect a space from negative energy. Salt is also supposed to be protective, as are stones like agate, jasper, quartz, hematite, obsidian, and many others.

But on a more physically practical note, is there any way to install a lock on your door? I'd take a picture of it and head to a local hardware store and see what can be done, if at all possible. My grandmother is a realtor an that's what she would recommend.

Hope you stay safe!!