...if your roof has any shallow pitches I'd ice and water dam all the way to the peak on that section with some neoprene.
Make sure you put ice/water shield where needed (the whole roof for low slope, valleys/bottom row if you see a lot of ice or snow).
How would you define "shallow" or "low"? E.g., does 5/12 pitch qualify? Thanks!
I can't provide a fraction for a pitch that would require full ice and water shielding, but let me put it this way and you can probably be the judge - if you can walk right up it, it needs ice and water shield IMO.
The reasoning behind that is as follows - if you have something that falls on your roof - most likely a stick, maybe with some leaves on it, that acts as the start of a dam to capture any additional organic material that catches on the stick till water can no longer flow past. Once water backs up and pools to a certain height (based on the slope) it can get up underneath the shingle above, once that happens if you don't have an ice and water shield laid down on your plywood its going to become soaked with water. The same thing happens in the winter where snow melt collects at the overhang and forms ice, the ice builds up during the freeze/thaw cycle as snow from the roof melts, flows down, and freezes at the bottom. That causes water to back up under the shingles as well. This is why ice and water dam is traditionally used in the valleys and bottom edge of all roofs.
So if you think that an unusually shaped stick could land on the roof and stay put under a light flow of water, you may want to consider ice and water dam on that slope all the way to the top (and crowned).
As a bonus, those areas that are stripped of shingles and fully ice and water shielded are good to go in a rain event, you don't need to put up a tarp once the ice and water dam is fully in place and there is no more exposed plywood. Usually its crunch time between removing shingles and laying them all down due to exposed plywood, and the application of an ice and water shield usually takes way less time than re-laying fresh shingles on a stripped roof.
Also a final tip - if you've got any skylights that may need replacement do it just before or during the roofing job. The skylight frame needs flashing which has to be integrated into the roofing job. Ditto for any solar panel plans you might have. Better to integrate it during the roofing job than to try and hack into your newly shingled roof and risk causing a major problem down the line.