Dua For Sehri or Starting Fasting :
This is the dua you will read when you have eaten your sehri and you are ready to full fill all instructions about Roza (Fast). And You are well known of thing from which you should be away. Like from now on you are not allowed to eat taste and do sin of ear, eyes and tongue. You should be clear to all these things. Because Roza is not a name of being hungry all the Day. You will have to do follow all instructions about the prevention in State of Rozadar (Person Who do fasting).
Dua of Aftar or Breaking Fast :
When you here the voice of Azaan of Magrib time then you are allowed to eat drink. You should first eat Date or drink water to break Roza because its sunnah, But if you want to drink some drink you are free to drink.