I am not from Pennsylvania and my experience with Building Inspectors is limited but, from what I see they are willing to work with those people who want to do the right thing. And they are willing to butt heads with those who want to butt heads. I can understand you not seeing the need for a permit from the apparent lack of permits on the neighboring houses.
I believe the permit cost is based on the value of the project. You doing the work yourself has kept the cost down. If the UCC utilizes the 2009 IRC then section R105 states that a permit is required and your roofing project doesn't fit under the exemptions of R105.2. The requirements for roofing are listed in Section R907 for roofing. If you want to look at the codes yourself you can go to the website below to view a PDF file of the code.
Once you find out what authority handles the building permits in your area; would you fill us in on some of the details?