She never does in my playthroughs. I fight her and her guards outside of the room. You don't trigger the goblins apart from one and you can go up the ladder on the left side. So outside of that room, Roa is totally save, besides, standing up on the balcony, the explosions wouldn't reach you. I always kill her. Just buy or steal the invisible potions beforehand.
She's done it in every playthrough that I've had; once even on her second attack when none of her companions had been killed, the blew everyone up.
Guessing Larian has coded in the AI to use barrelmancy whenever possible regardless or the outcome.
