Adding explosion force knockback on player

I mean this is completley up to you and how you want to design your game and physics/interactions.

This is also a pretty tricky thing to implement depending on how intricate you want the physics to be. I know that TF2 rocket jumping is very sophisticated and physics based and is not really that easy for a beginner to. WIth that said:

This comes down entierly to how you have designed your explosion and how you want to design this interaction.

I can think of one example where you let the explosion have a collider attached to it and if the player touches that collider you add some force to a rigidbody attached to the player.

Now that would be In some way the first layer, now it comes down to how many more layers you want to this. For example, you might want to check what "side" of the explosion the player is on so you shoot different directions depending on if you shoot the rocket behind your or in front of you.

You might also want to consider the direction of the rocket, a steeper angle will shoot the player further up and a smoother angle further forward.

If you share some more of your implementation and how you want the behaviour to be it would also be easier to give more concrete feedback.

Best of luck!