I understand vent is quite important for proper flushing of toilet. Without vent, toilet has problems flushing. In the U.S., you can see vent pipes coming out of roof. Those are shingle roofs. If roof is built with terra cotta tiles, I don't think vent pipes will go through tiles. What is done in this case about vent pipe?
Here in Burma, expensive houses all have terra cotta tiles. I don't see one single pipe coming out of any roof. I wonder if the toilets in the house just don't have vent.