If dog cowers when he comes in, that's all I'd need to see.
If so, rub the roomates nose in the dog chit, and let the dog see ya do that.
If the dogs sick, well ya gotta deal with that too, but, I've never had a sick dog act sheepish, tucked tail and avoidance, usually it's sad eyes, and the head rub on the leg, ya know, like... "Daddy, Help Me!"
The tucked tail and avaoidance, that usually does mean beat down... but, I'm surprised the dog would act that way with you
I hope he didn't beat him, hope ya get some answers, and the pooch feels better.