Preheat your oven to 400 degrees.
In a large bowl, whisk together balsamic vinegar, olive oil, honey, and garlic.
Add the zucchini, yellow squash, broccoli, bell pepper, and red onion to a rimmed sheet pan.
Top the vegetables with the diced chicken. Pour the balsamic mixture over everything, and toss to ensure all ingredients are well coated.
Sprinkle with Italian seasoning, salt, and pepper. Toss again to distribute the seasonings.
Spread the chicken and veggies into an even layer on the sheet pan.
Roast in your preheated oven for 10 minutes.
Add the tomatoes, toss everything, and spread into an even layer again.
Return the pan to the oven and roast for an additional 6 to 10 minutes.
Once done, remove from the oven, sprinkle with parsley, and serve immediately.