what i did was just tell my room mate the truth then bagged my diaper up and threw in the bin, then asked them NOT bring anyone back without asking me first to give me the chance hide my diapers. also i found wearing plastic pants over the top my diaper helped stop leaks and made me feel a lot more secure without using plastic sheets etc.
i too use a bodysuit or tight cycle shorts over my diaper keep them tight & help prevent leaks & the diaper showing through my clothes.