All right fine, I'll estimate the whole damn project.
So figure you're doing a roof- you said slate so It's going to be a shingle job, so that's almost definitely residential.
I'll shoot for a medium to large house/apartment building, average pitch I suppose... 1,500-2,000 square feet.
Split the difference and say five bucks per square foot- upwards of $7,500 for the material, then labor costs...
Again, that's estimating that you're looking for a whole-roof re-shingle.
If it's just patchwork, well not knowing anything about the damage I'd probably estimate the size at maybe 100-300 square feet maybe? Again, no idea how extensive it'd be.
That'd get us to around $500-$1500 material costs, call it a... four hour, two-man job? Construction union/competitive market wages.... $299 lets say.
Let's cast a really wide net and say anywhere from $1,000 to $1,900 size dependent.