"This powerful Resident Evil mainstay is rare but also powerful. In the Campaign, you'll encounter this weapon only once but you can use it freely in The Mercenaries. Any enemy you fire this weapon at will be instantly destroyed, along with anything around it. Since you have limited opportunities to fire the Rocket Launcher, however, you won't be able to fully enjoy its destructive capabilities."
In Campaign mode, the Rocket Launcher is obtained in Chapter 5 of Leon's story, inside Ada's helicopter. It has a small kiss mark on the loaded rocket, likely left by Ada to tease Leon or as a final mockery of Derek C. Simmons's obsession with her. The players will find the Rocket Launcher just as the mutated Simmons climbs onto the helipad of the Quad Tower, attempting to destroy Leon and Helena Harper one last time. To prevent Simmons from destroying the helipad, the player must grab the Rocket Launcher and shoot Simmons in the eye, finishing him once and for all. The Rocket Launcher will not appear in the player's inventory in the next playthrough, regardless if the player decides to use it or not. A secret medal can be obtained by finishing Simmons without using the rocket launcher.
In The Mercenaries, Chris Redfield wields a Rocket Launcher in his alternate costume. Unlike the weapon seen in the campaign mode, Chris' rocket launcher lacks a kiss mark. Coach also uses it in the PC version's The Mercenaries No Mercy. Again, the kiss mark is not present on Coach's rocket.
The model and ammunition can be seen in the game's files, as well as a specific reload animation, seen here .