* ¡Sal de mi dormitorio! This is a direct and fairly forceful translation. "Sal" is the imperative form of "salir" (to leave), "de" means "from," and "mi dormitorio" means "my dorm room." This is suitable for a friend or someone you're not particularly polite to.
* ¡Salga de mi habitación! This is a more formal version. "Salga" is the formal "usted" command of "salir," and "habitación" is a more general word for "room," which could encompass a dorm room. Use this for someone older or someone you want to treat with respect.
* ¡Fuera de mi dormitorio! This translates to "Out of my dorm room!" and is a more forceful and abrupt command.
* ¡Largo de mi residencia! This translates to "Get out of my residence!" "Residencia" is a more formal word for "dorm" and might be more appropriate if it's a more upscale dorm or a student residence hall.
The best option depends on your context and relationship with the person you're addressing. If you're talking to a close friend, the first option is probably fine. If it's a stranger or someone you need to be more respectful to, the second or fourth options would be better choices.