Is it the Radical Rodder gelding you bought a while back? He is a nice nice little horse.
A couple of things caught my attention the first being new saddle. Did you have it fitted? Does it have full Quarter Horse Bars?
The second is that you said he has never seen the cones out in his pasture before, and he looked scared. If he was he definately needs to be worked outside around different objects and some more ground work may be in order. You may have to get some help from your trainer as it is never good for a horse to succesfully buck off a rider. It can become a bad habit.
The best advice I can give you right now is to call your trainer and get some help as I know your horse is a young one if I remember correctly. They can help work you through it, and teach you how to prevent your horse from full out bucking. I would think they might want to show you how to busy his mind doing changes of direction, rollbacks, transition changes, etc etc so he is too busy to think about the buck and worry about the cones or anything else out in the riding pen.
Best of luck.