Make the marinade by mixing lime juice, garlic, ginger, red pepper flakes, cumin, salt, and pepper in a bowl.
Place the flank steak in a gallon bag and pour in the marinade. Close the bag and mix around to fully cover the steak. Let it sit in the refrigerator for at least 30 minutes and preferably a few hours.
Preheat the oven to 400ºF. Chop the mushrooms, tomatoes, and zucchini, then place on a large cooking sheet.
Pour over melted coconut oil and ensure all veggies have been covered. Sprinkle cilantro, lime juice, salt, and pepper over the veggies and mix around again.
Roast for 15-20 minutes, mixing around halfway through to ensure even cooking.
While the veggies roast, preheat the grill. When ready, remove steak from marinade and place on grill.
Grill steak on both sides for 8-10 minutes, then remove and let sit for 10 minutes before cutting.
Slice the steak, top with the roasted veggies, and serve!