'rough play' in normal English means very physical play. Exactly how physical would depend on the participants! So - it might include wrestling, and 'light' hitting. It usually wouldn't involve actual damage, and being play, if anyone was hurt, the other(s) would stop if they said so. Pokemon things are only ever loosely based on reality, so you can't always tell from the 'normal' word what the Pokemon meaning is...

Playing rough just mean that they are getting gritty and are not holding anything back. It could also be used to talk about kids or athletes who aren't necessarily playing fair.

That should mean 'the user attacks aggressively and violently'.