Heat oil in a large nonstick skillet over medium-high heat. Combine rosemary, garlic, 1/4 teaspoon salt, 1/4 teaspoon pepper, and lamb, tossing to coat. Add lamb mixture to pan; sauté 4 minutes or until done.
While lamb cooks, combine 1/4 teaspoon salt, cucumber, lemon juice, 1/8 teaspoon pepper, and yogurt. Divide lamb mixture evenly among each of 4 pitas, and drizzle with sauce.