Shading the roof should make very, very little practical difference. If it does, there is a problem with the roof insulation.
As a general rule, the roof cavity should be an almost-sealed box with convective insulation (e.g., fluffy fibreglass) on the base and reflective insulation (foil or similar) on top. Provided that there is sufficient convective insulation, the temperature inside the roof cavity doesn't really matter.
Ventilating the cavity has become very fashionable but it is practically useless - little better than a scam in most cases. It is nearly always cheaper and more effective to add another layer of insulation than it is to install a roof ventilation system. However, in climates where winter temperatures frequently drop well below zero, humidity in roof spaces becomes a serious issue. This is why roof ventilation is a necessity in many parts of the US.
(The geography of the US - essentially the gigantic arctic funnel formed by the Rockies on the western edge and the Appalachians along the eastern seaboard - leads to far greater seasonal variations than in most of the rest of the world.)
DB: I reckon panel shading would improve your situation by, on my rough calculation, approximately 0.00000321023%, give or take a few decimal places.