1. Heat oven to 450 degrees F. Coat two baking sheets with nonstick cooking spray.
2. Place cabbage on one prepared baking sheet, and onion and carrots on the second baking sheet. Brush with olive oil and season with 1/2 teaspoon of the salt and 1/8 teaspoon of the pepper. Roast vegetables at 450 degrees F for 20 minutes; rotate pans and roast for an additional 15 minutes. Drizzle with vinegar during last minute of cooking.
3. Meanwhile, heat a grill pan over medium-high heat. Season the pork with the remaining 1/4 teaspoon salt and 1/8 teaspoon pepper and grill for 2 minutes per side or until cooked through.
4. To serve, place the pork on individual plates and arrange vegetables over the top. Squeeze lemon over servings, if desired.