have you ever signed any mortgage documents? from where did you get an idea about raised percents for mortgage AFTER signing a document with says 3.25% for 30 years?
For a roof specifically, I have a roof insurance which cost 250$ for 2 years. and they fix any problems roof free. beside to roof insurance, there is a usual home insurance which covers a roof too.
and on top of this: buying a home on a market's bottom and then selling with higher price could bring you a lot of money. Why don't you consider this fact?