I hate roofing too!
Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.62.67.1520
What expansions, game packs, and stuff packs do you have installed? Get to Work, Toddler, Parenthood
Steps: How can we find the bug ourselves? Only available in the build mode
What happens when the bug occurs? When I build a half roof or a roof.
What do you expect to see? Cosmetic appearance
Have you installed any customization with the game, e.g. Custom Content or Mods? Never used.
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure
So the issue is pretty clear on the forum when it comes to roofs. When building a roof on a top level bringing the roof down to the lower lever will create an appearance that the roof is inside the house. I figured out that bringing the roof to a lower level will bring the roof inside the house. But, building a roof on a lower level does not affect the appearance on any level above which you are placing the roof.
Important! You can't bring the roof tiles up. The roof tiles can only move to the lower tile threshold. I tested this by basically building a roof on the ground. But, I can't bring the roof higher with the move tool. This is really important for occasions when there are no ceilings in some areas. I understand that making a room with no ceiling creates a lower level room on the higher parts of the house. So the roof tiles are bugged to not trim inside appearance even if it is applied. Because it thinks it's supposed to cover the entire area.
The solution as I described seems to be a good enough compromise for me. Move the lower level roofs up. But, that's not possible.