It's a form teasing

It depends on where you are. The original meaning is "to criticize or punish severely", but in North American now it just means "to tease, to make fun of in a good-natured way", as Danielle pointed out.

All the answers are correct. It is a form of teasing. Can be used to describe both friendly teasing and also intentionally negative insults. There is also an event called "a roast". in this event there is one main individual who is the subject of the party. A Bunch of people all take turns making jokes about the subject. At the end the subject gets to rebuttal them and make fun of them back. Usually roasts are good natured fun, but can sometimes be incredibly hostile. Usually the individual "getting roasted" is someone everybody likes and it can be considered a form of flattery to be roasted.

It means to make fun of, or riddicule another; to talk about somebody based on appearance, actions, or pesonalility. Most of the time done is a mean way.

a type of joke that focuses on teasing, poking fun, ruthlessly ridiculing, trash talking, or mocking someone. Roasting focuses on someones weakness, failures, insecurities, etc. Because of it's direct nature, 'Roasting', if taken to far, can result in really hurting someone's feelings to the point that they may cry