In a bowl, combine the minced garlic, olive oil, dried oregano, dried rosemary, salt, pepper, and lemon juice to create the lamb marinade.
Place the cubed lamb in the marinade and coat it evenly. Cover the bowl and refrigerate for at least 1 hour, or ideally overnight, to allow the flavors to meld.
Preheat your grill or a grill pan over medium-high heat.
Thread the marinated lamb onto skewers. If you're using wooden skewers, soak them in water for about 30 minutes before threading the lamb to prevent them from burning.
Grill the lamb skewers for about 8-10 minutes, turning occasionally, until they are cooked to your desired level of doneness.
While the lamb is cooking, prepare the tzatziki sauce. In a bowl, combine the Greek yogurt, grated cucumber, minced garlic, chopped dill, olive oil, salt, and pepper. Mix well and refrigerate until ready to use.
Warm the pitta bread in the oven or on the grill for a minute or two on each side.
To assemble the Greek lamb pittas, spread a generous amount of tzatziki sauce on each pitta bread. Top with slices of tomato, red onion, fresh lettuce leaves, and the grilled lamb.
Roll the pitta bread around the filling, securing it with parchment paper or aluminum foil if needed.
Serve your delicious Greek lamb pittas immediately with extra tzatziki sauce on the side, and enjoy!Feel free to customize your pittas with additional toppings like feta cheese, olives, or hot sauce, depending on your preferences.