Preheat oven to 400°. Place eggplant slices on a large rimmed baking sheet and rub both sides with oil. Season with paprika, salt, and pepper. Roast until golden and tender, 30-40 minutes. DO AHEAD: Eggplant can be roasted 1 day ahead. Cover and chill.
Whisk garlic, mayonnaise, and vinegar in a small bowl; set aside.
Toss scallions, herbs, beets, olives, capers, and oil in a medium bowl to combine.
Spread cut sides of focaccia with garlic mayo. Build sandwiches with focaccia, eggplant, feta, and beet salad.
Tags: beet, bonappetit, dinner, easy, eggplant, feta, lunch, nut-free, sandwich, summer, vegetarian
