Turn the oven to 190° C, air circulation and rack set at the middle.
Use an oven proof dish and add the beets. Pour on them the oil, sprinkle the coriander and season with ½ tsp of salt. Give them a toss and cook in the oven for about an hour and until well softened. Halfway through give them a toss.
Remove from the oven and allow to cool. Once cool, use gloves and grate them through the large holes of a grater box.
Add into your serving bowl the yoghurt along with the oregano and mint, vinegar and season with the remaining ½ tsp of salt and the pepper. Mix well and add the grated beets. Once again mix well and serve as a dip with pitta bread.