I live in an apartment with two roommates; three guys. One of my roommates ("T") has a small dog - not a problem in itself, but has brought problems.
Before moving in, my other roommate ("J") and I asked him how the dog behaved - does it yap, is it potty trained, clean etc. He responded no, yes and yes, respectively.
Within the first days of "T" and his dog movnig in, "J" and I quickly realised he yapped a lot. At people coming inside (including us), loud sounds in and out of the apt and even randomly.
Also, if I left my bedroom door open, the dog would waltz in and shit on the floor. This happened twice, to which my roommate, without apologizing or scolding the dog, just quietly cleaned the mess.
Over the last couple months the dog caught fleas. The fleas spread through the apartment. It got to the point where I was finding fleas on ME, outside of the apt.

We all went home for thanksgiving, and before I left I sprayed flea killer to let it sit for the week. Fortunately, "T" took care of the fleas while he was home and they seem to be gone.
However, the first day when we all came back, the dog shat in "J"s room. No apology.
Now "T" is away for a few days, he apparently couldn't take the dog with him and has asked us to take care of the dog. I think that it is his problem (he should put it in a kennel). and I am not willing to "do him a favor" considering the dog's behaviour.

Obviously at this point I have to take care of the dog until my roommate gets back.
How do I keep cool about this?
I'm trying to stay objective and not make an awkward living situation, but "J" and I agree that it's a problem.

Any advice would be appreciated