Marrakech is a low city, all terracotta and flat roofs, which means the rooftops belong to whoever climbs them. At sunset every terrace with a view becomes the best seat in town, and the only real decision is which kind of evening you are after: the theatre of the medina, the polish of the new town, or a quiet corner where the mountains do the talking.
For medina drama, stay inside the walls. The terraces around the Jemaa el-Fnaa and the Kasbah look straight out over the square's smoke and noise and the Koutoubia beyond, the whole restless heart of the old city spread beneath you. It is loud, it is chaotic, and at golden hour it is unforgettable — come early, because the good tables go to the patient.
For polish, go to Guéliz and Hivernage. The new-town rooftops trade medina chaos for cocktails, clean lines and a more international crowd — the sundowner as the French left it, dressed up and unhurried. This is the side of Marrakech that feels closer to the Riviera than the desert, and on the right evening that is exactly the mood you want.
For calm, get a little height and a little distance. The best quiet terraces look away from the crowds and toward the Atlas, so the show is the mountains turning pink rather than the square below. These are the perches for a slow drink and real conversation, and they are worth asking your riad to point you toward — the finest ones rarely advertise.
However you choose, the etiquette is the same. Arrive a good half-hour before sunset to claim the rail, dress a notch up from beach-casual, keep some cash for a tip that gets you a second round without a wait, and stay past the light — the blue half-hour after the sun has gone is when a Marrakech rooftop is at its most beautiful, and most people have already gone down to dinner.