An aileron roll done at low altitude is not as simple as it looks. Many years ago an Air Force general killed himself in a T-38 attempting to do one after departure. I witnessed a similar crash in a T-33 at an airshow in Michigan quite a few years ago. The nose has to be raised significantly before beginning the roll in order to prevent a downward vector upon completion. There is nothing particularly complex about what happened here. No use of flaps, no significant change in roll rate, etc. The pilot simply did not start with the nose far enough above the horizon, and thus ended up pointing toward the ground at an altitude from which he could not recover. It is an easy mistake, and even very good and experienced pilots have made it.