I now understand that I haven't seen the full potential of roofbuilding, this was awesome!

Hopefully that's changed in the future... even at a reduced speed, but I wouldn't be too surprised if it doesn't get changed because the roofs can go partially up a wall height, so could cause issues perhaps

Nope, they can not be walked upon

Nice
Was wondering if the roof slopes can double as terrain ramps?
Can your villagers walk on them?