What would be different if you had to defend yourself from someone who lives with you?

I've been living with a lottery of random strangers for the last several years as people come and go renting out rooms in the home I live in. Some of them have been good people, some have been assholes and one of them who I currently live with has been a totally unstable lunatic. I'd like more than anything to live without complete strangers who I do not choose as roommates but my financial situation won't allow currently.​My situation with this particularly unstable and angry stranger just got me thinking, how would things be different from a legal perspective if you were ever forced into a DGU against someone who lives in the same home as you? Does the castle doctrine apply to my private bedroom in some way that I am still allowed to protect it the same way I would protect my home if I lived alone?​Location: UtahNo, I don't in a million years want or anticipate having to shoot anyone. Ever. It's just an educational question. via /r/CCW http://bit.ly/2XTiPaR