Basically the devs never implemented a snow texture for roof trims, so they never get snow on them. In other words the roofs look very very ugly with detailed half-melted beautiful snow on the actual roof, and then sharp brown lines for the roof trim...
Same with the new veggie patches btw; they have no middle stage, they are either completely bare or fully covered. So when your garden is half covered with melting snow... the garden patches are bright white squares.