Are they right? Is it us or them?

Scabies is a contagious skin disease caused by a mite. I would say the room mates are to blame by not being very clean with themselves and their bed linens. Wash ALL the bedding and towels with Hot water and bleach. What the room mates do not understand but want to blame you for is their lack of cleanliness. Put the blame where it belongs, on them. You would of experienced the outbreak before them if you were to blame. Scabies were something our ancestors dealt with 100 years ago due to lack of Hygiene. Good luck!