When you press the green flag, the stats are rolled automatically. If you want to roll again, press "R". If you want to apply armor and HP, press "S".
This is a project for those playing by the original (or other rule sets that apply) D&D rules and want an easy way to create their character. This essentially does the exact same thing as the game (roll a 6-sided die 3 times to determine stats) so don't worry about that.