Hey Kusuma!

You can easily find your exam roll number of 10th boards in your class 10th Marksheet. It will be below the name category. Just read below name, you will find your roll number. In case you don't have your class 10th Marksheet, you can download it from digilocker easily. There you would have to use your aadhar for registering and you can easily acquire important documents from there. In case, for some reason you are not able to locate the roll number in your 10th Marksheet then you may look for the admit card of class 10th. In the admit card too, the roll number is written clearly.

Hope it helps!