The Rocket Propelled Grenade "RPG" does not have a lock-on function.

It is unlocked after a mission mid-way through the game, the player can carry up to 20 rockets. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? The only Customization options availible are Black Tint, Army Tint and LSPD Tint.

You can obtain a free RPG in the cannibal camp (the one Trevor can deliver hitchhikers to) in their weapons storage.