SPREAD eggplant, zucchini, squash, leeks and mushrooms onto bottoms of full-sheet pans (or onto bottom of half-sheet pan for trial recipe); brush with oil. Sprinkle with salt and pepper. Transfer vegetables to grill; cook on medium heat 2 min., turning occasionally. Return to sheet pan. Refrigerate until chilled.
CUT grilled vegetables into 1/2-inch dice. Toss with lettuce, tomatoes and dressing.
FOR each serving: Grill 1 tortilla 10 sec. on each side or just until warmed; transfer to work surface. Spread 2 Tbsp. hummus down center of tortilla to within 1 inch of edges; top with 1/2 cup vegetable mixture. Fold in opposite sides of tortilla, then roll up burrito-style. Cut diagonally in half.