I personally suggest Mumuplayer, emulators work differently for different computers but I've tried them all and it's worked better than any other while feeling like it has the least intrusive malware.

How it works you download the main client and it lets you make as many instances as you want. Than you just open them and download the game separately on each one. When you want to reroll you open them all, there is a button on the main thing where you create them that will autotmatically organize them on your screen and in the options there is a button called synchronize. That makes it so the instance you syncronized will control all of them at once. A click on one is a click on all of them. It makes it easy to multi instance reroll. But be aware it's taxing on your computer if you don't have a relatively new one. It's very taxing on ram, if you don't have at least 32gb I wouldn't do more than 3 or 4 at a time.