One of your roommates comes from a small rural town and the other is from a large city. does this factor affect their probability of experiencing a schizophrenic episode?

Yes, the urban population is at more risk of developing schizophrenia, which is basically an urban condition. The social environment, physical stresses, liabilities, etc., are very high in the urban society and these have been found to be directly linked to schizophrenia. So, my urban roommate is most likely to be affected by the disease.