I need an architect or structural engineer to design a roof for a 3x5m extension

I need a "quality design" for the roof of a basement extension that measures just under 3x5m. The roof must have a slight slope as the planner is scared that it will otherwise be used as a terrace. Further, a stair case that went from the ground floor back door to the garden needs to be incorporated into this design without creating a 3m walkway over the extension (overlooking issues). There is a 1100cm gap between the proposed extension side wall and the neighbouring boundary and Planner says she is happy for the staircase to go down this side; I.e. - abutting the extension wall. However, she wants it to start at a level lower than the door landing (c. 1x1m). The door in question will be immediately above the NW corner of the proposed extension, so the landing needs to be incorporated into the roof. Thanks.