To a large bowl, add the beetroot, sweet potato, salt, black pepper, garlic granules, smoked paprika, lemon zest, coriander, tahini, feta, eggs, and breadcrumbs. Mix until thoroughly combined. You should achieve a wet, sticky mixture that should just about come together when formed into a burger.
Next place a large frying pan over a low-medium heat and add around 1 cm (½ in) of oil. You need enough oil so the burgers are at least halfway covered with the oil when they are in the pan.
Once the oil is warm, cook the burgers for around 5 minutes per side or until cooked through and golden brown on the outside. Remove from the pan and drain excess oil on kitchen paper.
To prepare the tzatziki, add the Greek yoghurt, cucumber, garlic, mint, lemon juice, black pepper, and salt to a bowl and mix thoroughly. Refrigerate until ready to serve.
Place your beetroot patty onto a burger bun, top with tzatziki and rocket salad.