Good Q. I wouldn’t give a save for a spell unless it’s explicitly mentioned (I don’t think any of the base ones allow a save, but could see a very powerful spell that does).
I general, I think the higher default HP levels (of HP + STR), plus the genuine risks that casters take (I’ve had at least one mouse reduce themselves to zero WIL on a failed spell) balance out a spell like Fireball without a Save. But if you feel like it’s overpowered in your context, house rule away :)