If the round pen work you've done with him or other horses is all about getting them to "join up" with you,and follow you around like a puppy dog, and not about making him move out when you tell him too, then it is not going to be of much help.
I am sure Cherie is right in that you may have to learn how to give him a major spanking the next time HE decides where and when to stop.
I think that round pen work with the same frame of mind can be helpful, but that's in part because I cannot ride out much in the way of buvcking a horse might do if he were spanked good and hard.
If yoiu do chose to do more ground work, either in the round pen or on line, be sure that you are working a lot on getting him to go forward without attitude and without holding back. That is something I would try, since I am not so comfortable trying to fix it all on horseback.