How you take it off depends on which Roush shifter knob you're talking about.
Check out Kev's shifter install and if you have the same set-up it will be easy enough to figure out.
__________________
02 Stage 2 zinc yellow vert #7199
Roush Supercharger
SS Inserts
BBS RK18 x 8.5 (front)
BBS RK18 x 10 (rear)