A rogue is someone who operates outside of generally accepted norms.
It is an insult used to describe, in fairly mild terms, a person who cheats on their partner, or does not honour their end of a deal.
Often roguish personalities can be charming, which means that they often get away with their cavalier behaviour.
“Be careful when buy from that guy, he is known to be a rogue”
“That rogue just cheated on you again!”