Roofs aren't usually paper-thin. The tiles (or sheets, boards, or whatever else you plan to draw) have thickness, as does the (wooden/metal/plastic) understructure that they sit on. Thinking about the major parts that make up this roof should help you see where the lights and shadows can go.

I highly recommend looking at some reference photos for this sort of thing. Roofs aren't something you can draw well without having a basic understanding of how they work IRL.


Unrelated nitpicks, if you're interested:
The upper right part of the wall looks like it's at an angle because of the darker colours, but everything else suggests it's part of the same surface as the upper left.
The vending machine (?) seems to be facing in a different direction (mostly down to its width/depth ratio and the far side's white bit being much thinner than the near side's), but its stadow suggests that it's flat against the wall. The shadow of its legs also suggests the back of it is narrower than the front.
The air conditioning unit seems to be sitting a distance away from the wall because of where on the overhang it is. If it's meant to be attached to the house, it should probably be flush against the wall. If it's meant to be separated, then it could use a cast shadow to disambiguate this.
Speaking of cast shadows, that aircon pipe(?) looks pretty thick and should probably cast a shadow on the wall.
For an extra touch of realism, consider setting the doors and windows a little into the house rather than flush with the exterior wall, and perhaps raising the bottoms of the doors by a couple of pixels to show the threshold.