Let me get this straight. The roofer put a few scratches into a
birdbath that you say cost $250 when it was new by tossing shingles.
He offered to give you the full $250 provided you give him the
birdbath and you refused. Sure he shouldn't have made a mess on your
property. But assuming he cleaned it up and offered you full
replacement cost for the birdbath, exactly what do you expect? Talk
about being unrealistic.

And why didn't you just go over and talk to the neighbor when it first
became obvious debris was being deposited in your yard instead of
watching it happen?

What are your options now? You can sue the roofer and the property
owner in small claims court. That will waste a lot of time. And if
your very lucky, you'll get a judgement, most likely only against the
roofer, for the depreciated value of the birdbath, which will likely be
a lot less than $250. Then you'll find out you can't collect
anything because the roofer is judgement proof.