We had a new roof installed today and when I got home my husband was furious over the stress cracks in the ceiling and down the wall and the debris that fell inside as a result. Is this the contractors responsibility to fix?

By "stress cracks" I assume you mean cracks in the wall board or in the taped joints between wall board sections, correct? If so this is not structural, just cosmetic - that's the good news. It's easy to repair - just some spackle and paint touch up. As for who's responsible: check your contract and see what it says. If it's vague or ancillary repairs are not mentioned, you could talk to the roof contractor, but to be honest I doubt that get you anywhere. If I was the contractor I would point out that I didn't inspect the condition of your interior walls prior to doing the work, that cracks in wall board happen all the time and may not have been caused by the roof work (cracks can be caused by house settling, or expansion/contraction with the change of seasons), and I have no responsibility for the integrity of the wall construction. On the other hand, if the "stress cracks" are more significant - structural in nature - you may have good cause to complain and demand repair.

Its really simple, get 3 contractors to examine and give you free estimates for repair. This will give you an idea of the extent of the damages and a CAUSE(?) in case you have to approach the roofers. Of course you have already talked to the roofers about your concerns right?

Hope your roofer was licensed, bonded, and INSURED.

What do you mean exactly by new roof?
New shingles over old shingles?
New roof 4 x 8 plywood with shingles?
What kind of walls - old lath and plaster, or wallboard?
How old is the house?
Did they use nailguns or hammers?

I tend to side with the roofer, regardless. It isn't their job to inspect your house other than the integrity of the roof.

I have a dim memory of this happening around 1985 to a house built in 1918. Very professional roofer, but the plaster ceilings grew some cracks and sags. Our problem.