roof cracks

i don't have them yet but i was reading about how uv causes it. in is really uv or could it just be the heat then you get inside and turn the a/c on full blast?

if it is the uv them what about Rejex (i guess that's the best uv blocker on the market) or is there any wax with a higher uv index.

and then if the cracks get unsightly what about either painting the roof or having a wrap made for it. again i have no idea how well a wrap holds up (does anyone have an idea which is cheaper?)

the previous owner tinted the roof and i installed a sunshade to block the radiant heat so i can't see if i have cracks or not

i am just thinking and planning ahead