Are new roofs subject to pa sales tax?

Yes and no. The cost of the roofing materials (shingles) is subject to sales tax. The cost of the installation labor is not taxable. See this page on the PA Revenue site:

https://revenue-pa.custhelp.com/app/answers/detail/a_id/205

" Labor charges to install or repair items that become part of real estate are not taxable. This would include installation of such items as a water heater, boiler, or new roof."