Do you wanna go on mission?

"I only wish I'd gone on mission..." A story from start to End-game about Roy, Robin and Wally. A YJ version of do you want to build a snowman. Warning: Very sad at the end...I cried writing it. It is Endgame, so you know what's going to happen. Oneshot. No pairings. No OCs. No slash. FROZEN VERSE