Hi, I created a rocket commando, the other day, It is a beast, I use a 30% launcher damage relic, combined with a class mod that raise the damage on rockets and grenades, I use the sham 94% and the logans guns so I can refill rockets quick by just shooting the ground, I also swap weapons 100% faster, and reload 40% faster. He is a beast, seriously. If you need me to drop my commando gear for you I will.
The Topneaa costs 1 ammo to shoot, but since it's an Etech launcher, it has a huge splash damage, and a small splash damage. The large splash will never damage you, but if you are in the area of effect wearing a absorbtion shield, you'll get an ammo back. If you are within the small damage, it can kill you, but you'll absorb another ammo, most of the time.
You get 2 ammo back for every 1 you shoot. Sometimes the Topneaa doesn't even cost ammo, 2 for none.