revealing several characters at once

hello I am a wannabe board game designer and decided to use roll20 to make a prototype board game for playtesting with friends but i have run into the problem that i have several characters i want my playtesters to have but don't want to have to reveal them one by one is there a way to mass reveal characters (ex. player a gets the black set and player b gets the white set) i have a different set for each player because i don't want them to be able to move each others tokens

What do you mean be "reveal"? Move from the GM layer to the token layer? Assign a large group of characters to a single Player? The latter can be done with the API. Given your board game, does each piece they control need to have an attached character sheet? If they are just tokens, then each set could be attached to a single character journal, solely for the purposes of assigning control. This could be done rather quickly. More detail would help in answering this question.

Assign a large number of tokens to a player they don’t have character sheets but they have attributes because every token has an attack move and defense die (for most these are all the same thing)

Keith's suggestion is the best way to do that - this will need to be set up beforehand, for example make a character sheet called Blue, and one called Red. They don't need any Attributes assigned to them, just blank character sheets. Set all blue tokens to represent the character "Blue". Set all red tokens to represent the character "Red". When player 1 gains control of the blue tokens, open the Blue character sheet and give permission to player 1. They will now have control of all blue tokens. If you want to do this on the fly, with randomly selected tokens, you will need a Pro subscription and TokenMod.