Your asking about the shoulder roll, and no you dont want to roll in anticipation because you will be easy to set up that way. You need awesome reflexes to pull off a shoulder roll. Look up some shoulder roll drills on youtube if you dont have a coach who is experiecned with the roll. But honestly that will only get you so far, you really need a coach who knows what hes doing so he can correct when he sees you doing something wrong and all that.
So look some tuff up on youtube, play around with it while light sparring and keep an eye out for someone who has experience with the shoulder roll.