Answer: Palliative comparison.
Explanation: Palliative comparison is the comparison based on the characteristics that some other party or person can give worse result as compared to their own result. The individual doing this comparison states that their deed or work is not as bad as compared to someone else.
According to the situation mentioned in the question, Rohan is using the strategy of palliative comparison. He is covering his deviant nature by comparing it with other students who have destroyed more property than him. In this way he is trying to states than worsen deed are being done by other students than him , so he is not major defaulter.