The roof panels should be finished before installation, even if you only plan to paint them. Once installed, the angles of the attic roof will create hard-to-reach areas that will be difficult or impossible to finish later. This process can be complicated and confusing, so it's important to dry fit the panels onto the dollhouse before applying your wallpaper. Mistakes may happen, but they can be fixed, so try not to worry.
Make sure you understand how each panel fits together, so you know which side is up and down and avoid placing your wallpaper incorrectly. Use a pencil to mark the outside of the panels for reference. Be mindful of where the eaves are located. If you accidentally wallpaper the eaves, as I did on one of my left side panels shown in the second photo, you can always paint over the wallpaper once the roof is installed and you can see the eave.
I cut out the chimney slot on the right side panel, which was unnecessary since that slot is accessed from the outside rather than the inside. I will need to patch the wallpaper there later to cover it up. Keep this in mind to avoid making the same mistake. The middle triangle piece is not visible from any angle, so there's no need to wallpaper it; just paint it. Set these panels aside for now, as they cannot be installed until the tower is finished.
