Look along the line of the rafters that looks worst if you can, take a jack plane and plane the surface hopefully you will see good wood just under the surface, seal it up. now tap the areas of the trusses all over with a hammer with a hammer (preferably a mash) immediately behind, and in contact with the wood you are testing, it should have a good bounce to it and should not sound dull. any very small areas of damage can be plated each side, glued and spiked with appropriate nails, any bad ones best to replace, sorry...bosshogg,