Okay so i'm trying to make a weapon that can do multiple different things if certain things are done but that's not the problem i dont want all of the modifiers to be added to the base dice roll so I was wondering if it's possible to make multiple different damage rollables for the weapon kind of like how the Staff of Defense has the 2 rollable options for the 1d6 and the 1d8 im making a great axe if that matters for the question. sorry for lack on punctuation it's late.  

The two dice rolls for a quarterstaff are due to it having the Versatile property. All that does is add the d8 as an option to the d6 (since it’s the next die size up). If you were to add the Versatile property to a greataxe it would only ever add a d20 as an option in addition to the greataxe’s normal d12. If that’s what you want then there ya go, problem solved. If you want the second die roll to be anything other than a d20, then it is currently impossible.

Okay thank you i'll just keep in mind how the weapon works with until homebrew is further along

Happy to help.

I have another question. Is it possible to make something do 2 different types of damage in one damage roll?

Nope.