Over the years I've done a lot of roofing projects; the question is usually between tin and shingles. If you have a larger budget you might want to consider other options such as composite shake, but I will focus on the classic metal or asphalt. Both have their appeal and weaknesses. On both of my micro homes, I decided to go with tin roofing; that is my preferred choice. It can look great, is lighter than shingles, and I feel good having a solid metal roof over my head that will last a long time. On the other hand, shingles have their strengths as well. Architectural shingles look good! They don't last as long as tin, but they are easy to work with when it comes to flashing. If you want to add a skylight to your house, for example, that's worth considering. In my experience tin roofs go on much quicker that shingles.
That being said, I used two different tin roofing products for my homes. The first I built with a very high quality standing seam roof. The tin has a 26 gauge thickness (the lower the better), and all of the screws are hidden. Not having to rely on roofing screw gaskets is great for looks and functionality. The standing seam tin was more expensive, but in retrospect I would build with that every time. With the second build, I use normal "tough rib" tin. It came in sheets 3' wide, and went up quick. I spent more money getting a textured look on the tin, but from the ground you can't see the difference, so that turned out to be a waste.
When installing the windows on these houses, I used both recycled material and new. The first house I built with all recycled double pane windows from the seventies. They were very cheap, and I felt good about using recycled products. On the second build, I bought all new double pane, low-E, argon filled windows from Home Depot. In total I spent nearly $1,000 on the new windows, and had a bit of work to do building the window boxes. If I were to do it again, I would go new every time. In terms of the environment, what you gain by using recycled material is lost in efficiency tenfold. There is a major difference between a modern window, and windows that are decades old. Keep the old windows for greenhouses, and saunas; but in their defence, they do look much nicer.
I had a lot of fun with the doors. As a new builder, I framed the exterior door on the first build for a 30" door. Little did I know, the two common exterior door sizes are 32" and 36", and in the small town I live in it was not easy locating a well built 30" door. So, I had to build one. I set aside a few days to build a door and a jamb. I think the main door on a house is very important to look great, so I wanted to take some of the furniture experience I had, and build a very nice door out of padauk, sappelle, black walnut, wenge, and a window. Once I spent far too much money on the material, I laid it all down, and realised that the door was going to be far too heavy. I would need to beef up the framing just to hold it, so I opted for a cedar slab door.
On the second house, I simply bought a door, and am very happy with it. It is a normal metal door with an R value of 5. By comparison, the wooden door has an R value of 1.75. I also built an interior door. In my opinion, it's worth the time to learn how to build a door and jamb.