Hi Jai,
Anything inserted before you change the location settings (except the floor level) will stay where they originally were. The walls are set to extend to the roof, so if the roof is already in place at the original lower level, then it will stay where it was put and the walls will still only extend to the roof. When you delete the roof, the walls will extend to the wall height set in the Location settings, so when you then insert the roof again it will sit at the new wall height.
It is an interesting house design although only one photo is showing up for me (the second). Normally images are added by clicking the Additional Options at the lower left of the box where you type your message.
It will be good to see the completed model when it is finished.
All the best with it.
Allan