Legal Question in Criminal Law in California

Nothing is for certain. But you cannot be blamed for your roommate smoking marijuana. (Particularly if your roommate has a medical marijuana card) But the question is where does your roommate keep the marijuana? Do you actually share a room? Does your roommate keep marijuana in a room you share? How much marijuana does the roommate have? Where does your roommate get the marijuana? Is the marijuana kept in a locked container and your roommate has the only key?