Preheat oven to 450 F. Toss cauliflower, oil, marjoram, salt and pepper in a large bowl. Spread cauliflower on a baking sheet and roast until starting to soften and brown on the bottom, 15 to 20 minutes. Drizzle cauliflower with balsamic vinegar and top with cheese. Toss to combine and redistribute across baking sheet. Return to the oven for 5-10 minutes, until the cheese is melted and any excess moisture has evaporated.