in good shape repair the ones needing work. Sometimes there will be weak areas cause it is a poor grade of pine and you may get a large knot that breaks out between rafters. Most of my whole roof was loose cause of expansion and contraction. Stapling made it very tight and strong.
A solid wood roof can leak alot before the wood is damaged. In this case cause it is pine it is fine to reuse it and it was leaking for a while. If it had been plywood and leaking the plywood would be toast.
Because this home was plugged and cold not breath there was mold on the spruce but non on the pine, there is a resin or something in pine that resists rot fairly well.
I know didly squat about roofing and have learned the tiny bit I have here. with thanks. I checked with Certainteed and you don't have plywood over, it is not required, it may be recommended but it is not required. Comfortable enough to accept that from them.
If your boards were wide like 7-10 inches they should be ripped and they do recommend that. Use a cheap cheap rip blade and wear a face shield cause there is going to be shrapnel.