When Robert Simpson was growing up on the Northern Cheyenne Indian Reservation near Lame Deer, there came a time when he had a choice to make. And, because he made the right decision 21 years ago, this weekend Simpson will be competing in his fifth Indian National Finals Rodeo. “There wasn’t much to do on the Reservation, and most of the kids were getting in trouble,” Simpson said in a telephone interview earlier this week. “I took up saddle bronc riding when I was about 15, and it was rodeo that helped keep me on the straight road. It gave me something to work for.