Preheat oven to 450°F and place a large sheet pan in the oven to heat up for 5 minutes.
Pat steak cubes completely dry and toss with olive oil, Italian seasoning, salt, and pepper.
Carefully remove hot sheet pan from oven and spread steak cubes, mushrooms, and cherry tomatoes in a single layer.
Roast for 10-12 minutes for medium doneness, stirring once halfway through.
While steak cooks, mix together melted butter and minced garlic in a large bowl.
Remove pan from oven, immediately toss steak bites and vegetables with garlic butter, then sprinkle with fresh parsley before serving.