My friend is really into Fairy Tail and I watched a really good fight from it with Rogue and Sting vs Natsu and Gajeel. But he said that he didn't know who Rogue and Sting were. So I was wondering who they are and when they first showed up.
Rogue and Sting are members of the Sabertooth guild. They make their debut at the start of the Grand Magic Games arc, in anime episode 151 (Title: Sabertooth) and manga chapter 258 (Title: Sabertooth). Rogue is a Shadow Dragon Slayer, while Sting is a Light Dragon Slayer.