Correct me if I'm wrong, but I think you're mistaken with this definition you've provided. Basically, I don't think it makes sense.
Allow me to explain. Our events are:
Event 1: Roll 1
Event 2: Roll 3 or 4
Event 3: Roll 4 or 5
Therefore, the set of events is {[1], [3, 4], [4, 5]} ...