Hey Fazal!

From the question you have asked, it is difficult to understand what exactly your query is. The roll numbers are provided to a student by the school and in case if you are in 10th and 12th class, then you will get a roll number from the board you are enrolled in, like CBSE. Which class you are talking about or if you are referring to changing of schools or something else, you will have to specify a bit so that your query can be cleared. Please provide more details in your question and a bit more specification and then you may ask in the comment section. You may also repost your question after providing complete details.