Preheat the oven to 400 degrees. Spread the cauliflower on a baking sheet, drizzle with the oil and toss; season with salt and pepper. Bake until browned, about 20 minutes.
Meanwhile, in a small, heavy saucepan, melt the butter over medium-high heat. Cook, without stirring, until the butter is golden brown, about 6 minutes. Stir in the sage and remove from the heat.
In a large pot of boiling, salted water, cook the pasta until al dente. Reserve 1/2 cup of the cooking water, drain and return the pasta to the pot. Stir in the ham, cauliflower and reserved pasta cooking water. Stir in the sage butter and season with salt and pepper.