Preheat the oven to 400 degrees Fahrenheit (200 degrees Celsius).

On a large rimmed baking sheet, toss cauliflower florets with 1 tablespoon olive oil, salt, and pepper.

Spread cauliflower in a single layer and roast for 20 to 25 minutes until tender and edges are golden brown.

Remove cauliflower from the oven and allow it to cool to room temperature.

In a small bowl, whisk together the remaining 2 tablespoons olive oil, lemon juice, minced garlic, and dried oregano to create the dressing.

In a large mixing bowl, combine the cooled roasted cauliflower, cherry tomatoes, cucumber, Kalamata olives, red onion, and parsley.

Pour the dressing over the vegetable mixture and toss gently to coat.

Fold in the crumbled feta cheese and serve immediately or refrigerate.