No, the cost of the new roof is not eligible for the 30% credit. The rest of the installation and all equipment/panel costs are eligible for the 30%.
Qualified solar electric property costs.
Qualified solar
electric property costs are costs for property that uses solar
energy to generate electricity for use in your home located in the
United States. No costs relating to a solar panel or other
property installed as a roof (or portion thereof) will fail to qualify
solely because the property constitutes a structural component
of the structure on which it is installed. The home doesn't have to
be your main home.
https://www.irs.gov/pub/irs-dft/i5695--dft.pdf
