Approximately three years ago I had a private contractor work on the roof of our doublewide home. He built another roof on top of mine, filled the spaces in-between the rafters with foam insulation and then put a metal roof on top. We have noticed a weird looking place on the ceiling of one room and it has turned out to be water damage from a leaking roof. I was not able to get the original contractor that day so I called another company to look at it for me. They showed me how the built up roof was installed wrong and that the screws for the metal roof were in the wrong place. The new rafters should have been screwed to the old roof but since they were nailed they are now coming up. Long story short I called the original people that did the work and after several calls found that they are not willing to do anything about it. Would it be worth my time & money to hire a lawyer to sue him or do I just forget about and have someone else fix it?

You're going to have to get the roof fixed no matter what. You should have the new contractor give you a written statement of what was done wrong and what needs to be done to correct it. Then you send a copy of that statement to the original contractor by certified mail and a second copy by regular mail. You tell him in a cover letter that he did the work incorrectly and you give him 2 weeks to come repair his work. If he doesn't come to repair it then you have the new contractor perform the repairs and sue the old contractor for the cost.