What do you suggest if my friend said he is gonna take 8 roxicodone (oxycodone) 30mg at the same time. what is gonna happen to him.?

Very dangerous: Is your friend trying to harm himself? Call a suicide hotline in your area, or try to get your friend to go to the emergency room at once. Depending on how much he weighs and his tolerance for narcotics, this could be a dangerous dose. If he is taking it for severe pain, that's not a good idea--he needs to see a doctor and find out the cause of his pain and the best treatment.