Baseball sized hail would do anybody in, slate roof or not!
I’m blessed. The worst I’ve seen is bummy marbles sized hail, and that wreaked much havoc. I can’t imagine baseball sized hail.
A metal roof will hold up but it might not be very pretty afterwards.
I watched the storm on radar as it passed 1/2 mile to the west. The only way you ever want to see hail like this is the pictures on the weather forecast!