First, make sure trailer is NOT in to deep. I like the outside bunker tips on the front to be 6″ or so out of the water. When approaching trailer, approach slowly and as hull contacts bunks, cut power/take out of gear and let boat land on bunks. If not straight, reengage propeller. Steer right or left to straighten out hull and let it settle on bunks. That will straighten out hull almost all the time. Once straight, power up to the roller and you should be good to go. Let the bunks do their thing and they will line you up to drive up to the roller. When backing trailer in, I usually back it in initially deeper that needed to wet bunks which makes it easier to load. Then pull out until outside bunks are 6″, give or take, out of the water.
Good luck!