To reroll in Re:Dive without redownloading data you need to edit "jp.co.cygames.princessconnectredive.v2.playerprefs.xml". This file has a list of every asset the game has downloaded, which is why if you delete the whole shared_prefs folder the game will think there are no files downloaded even though they are right there. What you need to do is to delete the entries that have your account data.

If you are on emulator finish the tutorial and close the game. Turn on root and move the xml file to your PC (or just use an android text editor that can perform a search) and open it with Notepad or whatever. The lines you have to find and delete start with:
<string name="MHx5cg%3D%3D">
<string name="NnB%2FZDJpMHx5cg%3D%3D">
<string name="M3F1YSNkOnF0">

Basically 1 line containing M3F1YSNkOnF0 and 2 lines containing MHx5cg.

Delete them, save changes and make a copy of it. Turn off root, restart the emulator and you can now play without redownloading all data (small data download at the beginning can occur since that's your new account data). After you don't get what you wanted just use the copy you made instead of editing the file again. Repeat until you get what you want.