how to make a sliding veranda roof for sims 3?

the best way is to go and look at the different roofs in the game while in build mode and play around 

if you are looking for a glass roof, there isn't one in game and if there are houses out there with glass roofs it is surely Custom content 

check out some roof tutorials on youtube 🙂 

http://www.youtube.com/results?search_query=sims+3+roof+tutorials&oq=sims+3+roof+tutorials&gs_l=youtube.3..0.1630.8676.0.8889.25.17.3.5.8.2.735.4467.4j2j4j2j1j2j1.16.0...0.0...1ac.1.11.youtube.7c6R8gD55jQ 

Another idea, looking at that. It really just is the way that the camera is positioned. If you put those little walls on top of the pillars, going diagonally, it should create the same effect.