Well insulation is fine but my house doesn't have any because my roof is nipa..
Best advise I can give is install a ridge vent for the whole length of roof and large open eves..My eves are two meters wide at points so that the sun can never touch the walls.
If your "wooden trusses" are still in good shape,why not just give them a couple of coats of Solignum or Woodsaver?