Rocket passes through the player who fired it
Rockets, as well as other projectiles, that are fired by the player will pass through them as they make contact. This was done deliberately to prevent projectiles exploding inside their hosts, but means that (for example) a player will not be hit if they teleport into the path of a projectile that they have fired, or run out ahead of it.
This effect is negated if the player dies and then respawns while their ordnance is still in flight, because the new player is a different Thing (see section 3I of the BFG FAQ). They can then be damaged by their own projectiles.