I would roughly create it something like below probably, combining four roofs together. Are you familiar with methods like using slope arrows and/or roof join tool?
...actually easier to define these three sketchlines with negative slope. No need to use slope arrows then, but below as an example how you could use those.
I suspect that the transition between the sloped roofs and the flat roof will require a minimum vertical height to transition between the two different roofing membranes.
If that is the case, can you tell us what the elevation of the flat roof relative to the ground floor level?
Do you have a reflected ceiling plan showing the required interior ceiling heights?
I suspect that the roof transition between the sloped and flat roofs will require vertical walls which explains the lack of counter slopes on the left and top (see annotated plan)
-luc
