Sure, the ingame rocket smoke in Quake Live might look great in frag videos, but during the game itself it doesn’t really help you much. In the Q3 CPMA modification you could change the size of the rocket smoke trail, yet in Quake Live this isn’t possible. All you can do in Quake Live is just removing the ingame rocket smoke trail.
There, now you should be able to spam rockets all day long without having any smoke decrease the visibility of the game!
Read these Quake Live config customization tips for many more useful console commands.
Some other interesting cvars to disable more smoke are