Borgs, it is his choice to sleep in his truck, but you don't have to choose to deal with him freezing in a cold truck and his dog barking in the night and disturbing neighbors and 2 AM door bell rings and soup runs that disturb your roommate.
If he wants to make that choice, then I'd suggest you tell him to take his truck elsewhere and park.
You can set boundaries - - they are not rules for him. They don't have anything to do with what he can or cannot or should or should not do.
Boundaries are for you. One might be telling him: " if you want to visit me, you must be sober, and come inside and stay inside the house. However, you cannot park with your dog and sleep outside in the night by my house, and you cannot disturb me, my roommate or my neighbors in the night. If you leave my house, you will have to go elsewhere." And you can tell him if he doesn't respect that, you will have the police escort him elsewhere.
That is taking a pro-active step to protect you and yours, and that is a boundary.
Longer term, I am wondering what having this man in your life is doing for you. It may be time to rethink why you are staying in a relationship with him when he is so far from being able to act like a normal person.
You might want to pick up a copy of Melody Beattie's book CoDependent No more; it has been essential reading for many of us as we try to figure out why we're keeping someone so dysfunctional in our lifes, and how to take care of ourselves.
ShootingStar1