Gunsmith Weapons not There?

I keep seeing people say "GO TO BANSHEE TO GET THIS ROLL".. but it's never there for me. I've done Vespers so I know I can pick up the GL. Are they on rotation?

I keep seeing people say "GO TO BANSHEE TO GET THIS ROLL".. but it's never there for me. I've done Vespers so I know I can pick up the GL. Are they on rotation?