Just going to jump in here with my 2cents.
I have a 14 Roush stage 2 and JDM tune. I have 110,000 trouble free miles on mine now, and it gets used off-road. TRR, have my own short course and use it to Pre-Run for Baja (we race SXS) so its definitely not a street queen.
I still run stock driveshaft, stock oil pump, stock fuel pump, stock exhaust and still on stock cats...
Single biggest improvement from stock Roush was my JDM tune!!! Drive-ability, throttle response, acceleration all greatly improved. And better fuel mileage if you are just driving normal.
Couple things that you need to look at doing:
-JDM Tune
-Spark Plugs - NGK LT7iX (6510) (cooler heat range) and gapped for a blower
-Good fuel - I have only ever ran Shell 93. Its a busy station and always fresh. You Colorado guys probably don"t get the good stuff.
-Run the smaller Gates belt. I forget the number now. Its a pain in the ass to get on, but once you do, you will have no need for the Roush FEAD shield. I have a brand new one that I never installed once I switched to the smaller belt.
-Look into the bigger heat exchanger if you do a lot of low speed running/city driving (no airflow) or if its HOT like it is here in TX. Or if you tow like Dane.
As long as you are not trying to drag race from a dead stop on pavement, or you choose to stay in the throttle when it wheel-hops, there should be no need to replace the drive shaft. If you plan to use it in the dirt get Deavers, if it will see more pavement look into a traction bar.
The stock rear spring will hop the back of the truck off the ground the first time you romp on it..up to 40mph! They just cant take that kind of power, and it gets worse with a bigger tire.
I run a Deaver +3 with a 37 inch KM3, so I am aware that the second I feel the back hop, I get out of it. If you dont, shit will break!
To upgrade from Stage 1 to Stage 2 you can do it in your driveway with simple tools. The tune is the best part of it