In my original draft for a 'combat-ready Roll', she originally used a buster pistol, which is why I had her getting one from Santa Claus in last years' Christmas special. What prompted the switch to a melee weapon was just me wanting to mix things up a bit; Lots of Mega Man characters use guns and other projectile weapons, but so few get up close and personal. When I decided to put Enker in near the end of the first chapter, Roll using his weapon seemed like a fairly obvious route to take.