"8"-square tile
roofs on fancy apartment house terraces?"
I too have seen some nice ones.  I just pulled back a built-up roof to
reveil a terra cotta look tile roof with polychromatic boarders and designs.
My best guess is that it lasted fifty years before someone decided it needed
coal tar cover.  I too would love to more about the types of grout and
maintenance for these patio-roofs.
Best,
Leland