If I live with roommates, is there anything I can do to prevent them from opening (or breaking in to) my room, planting drugs, and calling the cops?
I know this may be a little paranoid, but I read this story and it got me thinking....
My solution to this question is to make sure there are credible sources of evidence of your character.
Make sure that anyone who knows you, knows that you never do drugs. Additionally, never do drugs. Whenever somebody inquires if you would like to do drugs, reply in the negative. Several years of doing this will establish that it is not in your character to do drugs, something that could be introduced in an eventual trial.
In the above events also make it clear that you never buy or sell drugs. That will give you a character of being a good person. Also, never do anything dishonest and just make sure there is nobody who would negatively testify against your character in a credible manner.
Next purchase a secure door. Afterwards install a 24 hr security camera in the room. Make sure there are no blind spots.
Lastly, my suggestion is to never let anyone but yourself into the room. Make sure that everyone in your house knows this and anybody else you can tell. Before moving into the room, get the room professionally cleared of any traces of DNA or finger prints. From now on, only your biological traces should be in there.
None of this is legal advice, just my speculation.
You can prevent them from breaking into your room by getting a lock system that can't be breached. This doesn't prevent the second - planting drugs - concern because they could slide the drugs through the door or blow them in through a vent. Perhaps you can tie up your roommates when you are not home. As for calling the cops, I can't think of a way to prevent your roommates from calling the cops. Any method that I can come up with starts to sound like interfering with an emergency call which is a crime itself.
Preventing this stuff as the question asks is impossible.
I never thought of a roommate trying to frame someone else before. I agree with Viktor, that installing a security camera would be a good idea. If you ever see one of them entering your room, I would call a criminal lawyer for advice.
Can you prevent them from hiding drugs in your room and calling the cops? Probably not.
On the other hand, in many places framing someone for drug possession is a much more serious crime than possessing drugs. While the cops don't like it if you use drugs, they absolutely hate it when someone interferes with their business.
Instead of having a very secure door in your room you might consider having no secure door at all, in which case it would be hard to prove beyond reasonable doubt that these drugs are yours (actually, since they are not yours, it should be impossible to prove beyond reasonable doubt).
After you're arrested, you could have your lawyer have your hair for drug use. It will show that you haven't done any drugs in the past 90 days. It's easy for somebody to frame somebody else for a crime. But if you're careful when dealing with others to not make them angry with you or hate you, you shouldn't have any problems.