Roommates and their Dogs?

I just moved into a house with my roommate he has two dogs. One a puppy the other 2 years old. The issue is that i am only willing to walk them one time in the morning, and when i get home, not every two-hours or so. If i don't walk them they go to the bathroom all over the house and i don't notice. ( It seems a little to me that he did not train them too well if they can't communicate when they have to go to the bathroom ) They are not my dogs but i really like animals, so i feel guilty leaving them in their cages when i come home from work/school prior to him. My roommate wants me to either walk them every two hours or just leave them in their cages until he arrives. I need a solution where we are both happy. The backyard is not fenced but hee refuses to get a stake, and i do not feel comfortable just leaving them in their kennels. So i really would like to find a medium.