What you need is the smallest jump you can find, not a roller, but a jump thats about 30-40 cm high and has a smooth knuckle so it doesnt matter how far you fly.
Hit the jump a couple of time straight and slowly. Until you figure out the right speed. Then walk back up, take your skis off, and jump a 180 on flat ground on your ski boots. Do it 20 times. Memorize the motion. Then put your skis back on and hit the jump slowly and repeat the exact same motion.
The first time you will land sideways but just slide it out. Walk back up. Take your skis off again, jump a few 180s on flat ground, put your skis back on and try it on the kicker. After a couple of times you will have it.
Once you have it start doing it off little bumps and off the side of the slope. After a while you'll be able to do them off flat ground and off big kickers. They will become really easy, but you gotta practice and practice and practice.