The 1v roof pentagon struts could also be longer or shorter, depending on your preference, but, it probably doesn't make sense for them to be shorter than the dome deck pentagon struts. If they were shorter, the shade structure would have a smaller roof than the base, and the walls would lean inwards. If they are larger than the dome deck pentagon struts then the roof will be bigger than the deck, which might not be too bad. Then the roof will cast a bigger shadow and be a better shade cover. But, of course, the walls would lean outward. It might mislead someone into thinking the wooden deck is larger than it really is and they might step off the deck! I made my top pentagon the same size as the dome deck pentagon struts so that the walls are vertical.
The 1v roof radial struts need to be long enough so that the roof is higher than the roof pentagon. It needs to be enough higher so that the structure is rigid. For example, the center of the roof should be at least 1 foot higher than the roof pentagon struts. In a regular 1v, the center of the roof is higher than perhaps you want for the shade structure. A high roof is more likely to catch the wind.
In the end, I just took the conduit left over after cutting the roof pentagon struts and flattened the ends and called those the radial roof struts. That made for a lower roof than I would have had if the radial roof struts were the same length as the roof pentagon struts, and it had the advantage of eliminating all waste for those struts.