If the roof is still solid you want to go in thru the ceiling. Remove the ceiling boards and take a look at what is broken. If you are not going to load weight on the roof again you may be able to fasten "helpers" where ever the truss or rafter member is broken.
Straighten out the broken piece if necessary use a jack and wide dead-man for support. Once the truss-rafter is straightened, stiffen it by fastening another like size stick of wood the entire length. If you need to you can block in all sides of the truss.
If the truss is shattered build another like size one and replace it or install it right next to the broken one. Installing a new truss and getting a tight roof over it can be tricky.
You will find plastic stretched out above the ceiling. supporting the insulation. If your lucky it will be rolled insulation. If its blown insulation you might be able to shift it over another section of ceiling while you make repairs. Either way don't neglect to repair the vapor barrier plastic and replace the insulation, prior to closing up the ceiling. Be sure to take precautions and observe safety practices
when you handle insulation
Replace the ceiling with light weight drywall boards. Finish as you would any other ceiling.