Rocket spawns at end of rocket launcher barrel, line traces and vector math will give you the required direction and angle to hit the target, you can also adjust the launcher aim via aim offset so the barrel lines up with the target at different distances.
One method is to run a line trace from the camera (center of screen) to the intended target resulting in location and distance, point “A”,
then calculate the difference in angle from the tip of the barrel to point “A” ,
depending on the distance from the player this angle maybe noticeably different from the barrels “forward vector” (think counter strike had this for years, hidden by bullet speed and muzzle flash)
You can use an “aim offset” to adjust the upper body of the character to aim the launcher on this new forward vector, lot of different ways to either calculate or use vector functions to find an acceptable solution.