Roommates are not the most hand-hygienic. how is hand washing a preventative measure when they are touching the same food items? e.g. making toast, i have to touch the bread and the jelly jar regardless. does my immune system take care of the rest?

VOVID-19 prevention: Assuming your roommates are not self isolated, i.e. they are out some of the time, the most important thing is that they sociually distance themselves and wear masks when near other people. If you're not confident about this, you're right they should wash hands carefully. But contacting food etc is very low risk. Frequent washing or hand santizer are more important, and keep hands away from face.