Well, step #1 is to contact the roofer and have him come out so you can show him the deficiencies. Step #2 is to track down the written contract between your dad and the roofer to see exactly what and what wasn't included in the work. For all you or I know, there may have been something in the fine print stating that the roofer was only responsible for putting on the shingles and NOTHING ELSE. Step #3, contact the bank. There's no way in He** they are going to want to be loaning out money for subpar work. They can put some pressure on the roofer to get this done right. For now, that's what I would do. If none of that works, you will have to retain a lawyer and fight this thing. Take lots of pics and document everything.