The square footage price will depend on the quality level of products that you choose, whether very high end or average....anything from $175 to $275-300. In any given re-model or re-build, you need to consult a good Construction person, make sure you get all the required permits from the City, so that its all done as per code, and that will also add value to your property if you ever decide to sell. The Construction person will help by drawing up architectural plans, that also need to be approved by the City of Cupertino. There are several different kinds of roofs too, so price again will depend on what you choose.
I live and work with Coldwell Banker in Cupertino, have my kids in local schools. I have good vendor resources, construction persons and a good roofer. Please call me, no strings attached, i will be happy to help you in any way I can.
Be well and safe, regards,
Nina Daruwalla; 408-7773823