"If I got caught growing marijuana, would my roommates and landlord be arrested and convicted as well?"

There are many variables to a decision to prosecute. It all depends on the extent of your roommate and landlord's involvement, their access, and other factors. But your roommate specially, is vulnerable to being charged. As to your landlord, it all depends on facts like: was there police activity on that property , or the landlord's knowledge of the illegal activity.

If your landlord and roommates had no knowledge of the grow, then they should not be able to be found guilty of that offense. Missouri requires knowledge for a conviction. However, if your roommates blindly ignored the growing plants in the yard or the participated in consuming the fruits of that grow, then they still could be convicted.

Mr. Randazzo is correct that knowledge is required. However since the Prosecutor can't go through your roommates' and landlord's memory they could be charged anyway. Please remember that the prosecutor has plenty of ways to prove knowledge other than a confession and even when someone else is claiming to be the sole person in charge. It can become a jury question and juries in Outstate Missouri can be very conservative. In your hypothetical certainly they might be perfectly safe. In reality I fear the testimony of some police officer: "Once I entered the home I immediately smelled the presence of marijuana. It is in my expert opinion that no one could have stayed in the house without knowing of it's presence..."

The prosecutor could charge you all.