Well it is the same with our house, the hat is key to both look and performance. We knew pretty early on in the planning process that we wanted to go with a standing metal seam roof. This was for a few reasons, the first and most important was solar reflective index (SRI) which is a measure of a surface’s ability to reflect solar heat. I wrote more about this here.
One of the important pieces to a good roof is sealing all the protrusions through the roof like vents and the chimney. Though the chimney rises on the outside of the house we still worked hard to seal the area where it penetrated the roof as the roof structure is wood and we didn't want water seeping and compromising the framework.
And so far this spring/summer we have had some quite warm days and that house is cool as a cucumber!!