As someone who has had roof replacements 3 times, no one has told me of the debris that could come in. I'd think to do your best in friendly negotiations. Anything further and it could get costly to litigate and may be deemed a run of the mill peril of construction.

I would also note, I know you mention a nice relationship with the guy. Consider what you pay in rent vs whatever the market is now. I recall a post maybe 6 months ago where someone fought the landlord over something relatively small (not saying your damage is small, I don't know the extent), but it was like $1,000. So his lease wasn't renewed and found he couldn't get an apartment for like kind and quality for less than $500 more a month... He fought the landlord over $1,000 and now had to pay $6,000 more a year in rent. He got the $1,000 but I don't think it worked out in his favor.