One of the issues with current dice roller apps is that they roll a bunch of different dice at the same time, and you must figure out where the dice you want are. This also opens the door to cheating since you can just pick the highest rolled dice in these apps. They look like this:
My dice roller will allow you to to pick the size of the dice you want and then roll 6 of them but you have to declare your choice before you hit the roll button so there is no cheating.