Thanks for playing! The rocket launcher explosion applies a knockback velocity that is additive to your current velocity, so if you rocket jump during the apex/falling portion of your jump you dont really go no-where. you also need to hold the jump key otherwise you will lose a lot of vertical momentum when you release it, which your comment made me realize really doesnt make any fucking sense for a rocket jump.
There is a jump buffer with a 0.12 second buffer window, but there is currently no buffer related to aim. Finicky is not the goal so I'll spend some time tweaking the values of the movement.
I will see if I can make jumping / rocket jumping feel better / more intuitive and reply here if i get an updated build out. Feedback is much appreciated!