Let me make some things clear before we start. Yes, this achievement is MISSABLE if you don't pay enough attention and if you are stupid enough to jump in and out to other players game, just as i did. If you did so and miss the Denial, Anger, Initiative mission and the chance to speak with Roland, there is still another way to unlock this achievement.
First, make a new profile on your Xbox 360, and start a new split screen game. Make your dummy as the host, and join with your main profile into his game. Progress until the first fast Travel console become active (takes around 30 minutes of gameplay, right after Hammerlock repairs Claptrap. Then travel to the Unassuming Docks, and start playing the main story until you reach the point to meet with Roland.
It requires about an hour to do so, but at least you don't have to beg other people to do it with you, nor hunt for online games where tjhis mission is active.