Place onion and garlic into food processor bowl. Process until finely chopped.
Add remaining ingredients and pulse until well blended.
Prepare the Panko Crusted Zucchini
Stir panko, salt and pepper together in small bowl.
Coat a large skillet with olive oil and place over medium heat.
Working carefully and with one piece at a time, coat top and bottom of each zucchini piece with flax mixture, followed by panko mixture.
Transfer to skillet and cook until golden brown on each side, about 5 minutes per side, turning very gently between sides.
Remove from skillet and transfer to a plate.
Assemble the Sandwiches
Divide zucchini slices and arrange on bottom half of rolls.
Top zucchini slices with ricotta, then with sauce.
Recipe Notes
While flax seeds work as a great egg substitute, they don't bind quite as well as eggs. Handle your zucchini carefully during frying, and do it in batches if necessary, to avoid the panko coating flaking off.