Here's how to reroll without downloading data again For Android users only. (might not work for some)
1. Go to File Manager->Internal Storage->Android->Data then rename "jp.co.ideafplus.hypnosismicarb" by adding one letter or number (eg. jp.co.ideafplus.hypnosismicarb1) then save.
2. Go to your phone settings and go to App Manager (or something like that) and find HypnosisMic.
3. Clear data
4. Go back to File Manager->Internal Storage->Android->Data and then delete the additional number or letter from the file you renamed earlier, in other words, return the file name from its original name. Save.
6. You can repeat this if you are not satisfied with the gacha result