Astromech have action that says remove this die to turn a vehicle die to any side.. So my dices of astromech support and vehicle are on their cards waiting to get rolled, so do i just remove astromech and place vehicle to any side in pool or both of them have to be in pool to remove astromech.. Or only vehicle have to be in pool?

You can't interact with dice that aren't in the pool.

No, both the support and the Astromech need to be in your pool to be used. You remove Astromech, put it back on it's card and then flip your vehicle die to whatever side you want. Again both these dice need to be active/in your pool to use.

Dice that are not in pool does not exist rule-wise (source: RR - set aside zone).