Firstly, make a two story lot. Make sure the building a perfect square and even in number of squares. I’ve used 8 for the tutorial.
Build your guide walls one foundation piece and one wall height, place guide walls diagonally as shown.
Next, bring up the cheat console (ctrl, alt & C) and type in the cheat
boolprop constrainfloorelevation false
Using the level terrain tool, drag from the front guide wall, across to the rear guide wall, lowering the second story level of walls as shown.
Add the pattern to your roof using floortiles, low fencing etc..you do not have to have skylights or an overhang, make any pattern you like.
Level down to the ground and underneath, using coloured floortiles, recreate the shape as shown. (we're mimiking the shape of the roof on the floor for reference)
Squares inside each other, getting 1 square smaller all the way around, also place the low fencing diagonally. This is to be used as a guide and will be removed later.
Choosing the first corner stair inside the lot (marked in green), lower the corner of each square with the lower terrain tool by 1 click (If you're not using an overhang, start lowering 1 square in from the edge of the inside of tthe lot)
Using the level terrain tool, drag from the lowered square and level the largest carpeted square inside the lot.
Next, move in to the next square diagonally (as shown). Lower this square by 1 click in each corner also.
Repeat the same process as before, drag the level terrain tool from the lowered square to fill up the inner square (square marked in pink with floortiles)
Continue the pattern along the diagonal – lower square by 1 click each corner
And drag across from lowered square with the level terrain tool
Same again – lower 1 click each corner
Once you’ve levelled the 2x2 square, use the lower terrain tool and lower the centre of the 2x2 square by 1 click
You should then see something resembling below when you level up
Using the level terrain tool, drag from one guide wall to the other, to flatten the roof area
Level down and using the level terrain tool, flatten the ground underneath the lot.
The roof is now complete!!
For steeper roofs, you can lower the squares by 2 or 3 clicks at each stage.
Remove the carpeting and fencing from the ground underneath and the guide walls.
Don’t forget to turn off the cheat
boolprop constrainfloorelevation true