Hello, i don't know if the question was asked before, but will i be able to fail a roll if i choose to?
It's against the basic rules of a roleplaying game with dices, which are the outcome of your actions are decided by rolling dices against calculated odds.
If you can choose to fail, you should also be able to choose to succeed, in which case it just becomes a branching story like Detroit become human or Life is strange, which is great for this genre of games. But BG3 is following other tabletop rules and choosing to fail isn't an option.
That being said, there might be a way to do it with the console, if Larian allows it in the future.