When you’re starting out in the game, you will be able to find Resurrection scrolls all throughout the world. There’s no permadeath setting at play here, so you will be able to revive them if the need arises.
However, don’t worry if this does happen. Whether you make a miscalculated move, or you’re outplayed by the enemy AI, you will inevitably have one of your characters die. It’s going to happen to everyone at some point in Divinity: Original Sin 2.