There are a number of different 4 inch kits from Rough Country and not all of them come with all the parts needed, namely new trackbars and control arms.
Track bars hold the axle in the middle of the vehicle from left to right, while the control arms hold them in a front to back, but also at the correct angle with respect to the drive shafts and steering components. If these are too short the axle sits at the wrong angle causing excessive stress on the drive shaft linkages, as well as putting the wrong stress on steering components, making the vehicle drive a bit squirrely.
These don't necessarily need to be adjustable (it's a good idea though), but they do need to be the correct length for the lift. I see some of the Rough Country kits come with new ones and some don't. Do you know which exact kit you got?
I like those wheels on the black jeep btw, that opens possibilities if I ever get a black one, which are generally too boring for me.