Occasionally, I roll for players. For example, I have a player that cant always roll on roll20. So I click on her character sheet for her. I know its setup properly. I know the halfling luck checkbox is set. But ive noticed then when I roll as the DM by clicking on it, its not doing it. Ive seen this by a few nat 1's, but also by hghlighting over and seeing its not rerolling 1's. Interestly enough, when I give myself "player access", and rejoin as player it does roll properly.