I used on on my last bike (BMW R1200CLC). It essentially raised the airflow about 2-3".
No experience using one on the Rocket, but I did find raising the windshield as much as possible helped.
I removed two bolts at the bottom of the windscreen and reinstalled them above the lower adjusting bolt to allow a tad extra height adjustment.
Try moving the whole screen up or down (adjustment) before you buy it.
A friend bought one and it fit him but not me.
Lower the scereen to flow the wind to your shoulders
If you already have a TRIUMPH mount, a second screen would be better, it you don't like the OEM.
Clearview will make you one as big as you want if you have the OEM hardware mount. They are in Colorado. I had one for my Trophy that was 2 inches higher than OEM with a curve that made the rider almost weather proof.
I have a friend that is 6' 6" and they made him a barn door for his sport bike.
It looks crappy (IMO) but he is happy and has full protection. Giant screen on small bike, but he's a large dude and the sport bike looks tiny on him and he likes it.
BTW...
I found that the OEM is not a screen to be full protection.
My mount allows for tilt back and forward and up and down from the "default" position.
Also ride with it lowered as far as you can and tilted back a bit.
I had some brackets made that allow the standard screen to be tilted backwards - then I cut 4 inches off the top. The result gives me good weather protection for chest and arms but my head is in relatively clean air so doesn't get battered which the standard Roadster touring screen was doing so much that I couldn't see straight.
Mike