01 - Heat a grill pan or skillet over medium-high heat until hot.
02 - Toss zucchini, bell pepper, red onion, and eggplant with olive oil, salt, and pepper to coat evenly.
03 - Cook vegetables on the grill pan for 2 to 3 minutes per side until tender and lightly charred. Remove and set aside.
04 - Slice ciabatta rolls in half and spread 1 tablespoon pesto on the bottom half of each.
05 - Arrange grilled vegetables, mozzarella slices, and tomato slices on the pesto-coated bread halves. Cover with the top halves of the rolls.
06 - Place assembled paninis in a preheated panini press or grill pan. Press and cook for 3 to 4 minutes until the bread is golden and cheese has melted.
07 - Remove paninis from heat, cut in half, and serve warm.