Salvaged wood timber is an excellent option for building roof trusses. If you buy salvaged timbers through an architect for a custom home like this they will be pricey of course. But timbers like these can also be obtained cheaply or even for free if you do the work yourself.
Years ago my friends and I volunteered about two weeks to help tear down an old World War 2 era warehouse at the airport. For our efforts we obtained enough rock hard old growth douglas fir wood to build a 1,000 sq. ft. house for free. The deal included full 2” thick 2”x12” joists and 2”x4” studs. You can’t buy newly sawn wood so strong. It was a lot of hot, hard crowbar work, but also a lot of personal satisfaction.
By the way, the salvage company we worked for did all the work negotiating the contract, getting insurance, etc. He made the most beautiful antique custom barns I’ve ever seen. They were truly works of art for rich horse owners. (This is a potential business opportunity if you’re interested.)