I don't understand your comment about the effect of latitude. I live in the USA, which has a quite different climate from where you're from (Europe, I'd guess). There are large regions of the country that get quite hot in the summer (35 C) for months, but can get very cold in the winter (-5C or so). In this region, early winter snowfall typically blankets roofs for all of the cold months, so the color of the roof is unimportant. After the snow, it'll be white! Now, in the summer, these regions face the same cooling problems as the southern parts of the nation, so a high albedo paint on the roof is a good idea.
I'm afraid I'm also at a loss as to your comment concerning tall buildings. Radiative heating scales with the surface area exposed to the radiation, not the volume (unless the object is partially transparent -- definitely not the case for buildings). The energy delivered by the sun will be lessened by about the same factor for a 10 story building as for a one story building. There may be additional exposure from the sides of the building, but this generally occurs outside the hottest time of the day. Moreover, old buildings would often use tar on the roof. It helped to seal out water and was cheap. But it's black and can really cause the place to heat up.