Ok here we go...
First start by opening both Illustrator and Photoshop...
go into illustrator and select the polygon tool.
then right click on your stage and pick a size that will be about 1.5 times larger then what you will want it to be at the end: Im going for about 50 pxls so I will make this 200 with 12 sides:
now off set path by a a number that is a small percentage of the total, but do not go too small, I went with -10:
from here repeat the last step till you get the polygon to be very close to a dot, but while you inset the path you need to drop the distance between the lines I did it like this:
-3 and filled with black
now draw a line from each point on the edges to the opposite side.
Make a new image in Photoshop, i did 600 by 600 to make sure that i have enough space to work things.
paste a texture that you want the roof to be... it does not need to be HD infact it kinda helps if it is smaller...
now duplicate and flip the layer then merge:
now go to free transform and grab the two top points, and put then together in the middle then grab the bottom ones and bring them straight up, then use the anchors and make it round out:
Now duplicate flip and merge:
make a selection that is in the shape of a hour glass and copy and paste then repeat by 45 degrees dont worry about how lined up they are it gives it some character, just try to keep the lines even.
Now set a drop shadow, and inner bevel chissel soft, change the bevel light settings to soft light for the hightlight and mess with the darkness ont he multiply at this point scale by 50%
Paste your wireframe from illustrator over the image of the roof and set opacity to multiply and mess with the %, then select the roof layer and the magic wand and select everything outside of the roof graphic.
select the wireframe layer and delete the selection the scale by 50% or so... and your done
If you want to get more detailed before you do any resizing you replicate the last step of selecting all of the outside of the roof, then select inverse, now make your selection contract by -10, or what ever your first interval was on the wireframe, and copy then paste in a new layer! after that paste the layer style from the bottom layer and paste it on the new one... then continue doing these steps for each interval that you did on your wireframe.
it makes the roof itself over 20 layers but it well worth it for depth effect, and being able to completely control shadows, when ever I do building construction I make a ridiculous amount of layers its hard to keep track of but give it a shot, you can make something 2d look like it has 4 or 5 stories to it, and be noticeably different then the 1 to 2 story houses or building structures.
SORRY FOR ANY MISTAKES I DID THIS ON MY 20 MIN LUNCH BREAK!