Cook the pasta according to the package directions. Drain, reserving ¾ cup of the cooking water, and return the pasta to the pot.
Meanwhile, cook the bacon in a large skillet over medium-high heat until crisp, 6 to 8 minutes. Transfer to a paper towel-lined plate and crumble.
Add the sage to the drippings in the skillet and cook over medium heat, turning once, until crisp, 1 to 2 minutes. Transfer to the plate with the bacon.
Add the cauliflower, ¼ cup water, and ¼ teaspoon each salt and pepper to the drippings in the skillet and cook, covered, for 2 minutes.
Uncover and cook, tossing frequently, until golden and tender, 3 to 4 minutes more.
Add the reserved pasta water and ½ cup pecorino to the pasta; toss until creamy. Add the cauliflower, sage, and bacon and toss. Sprinkle with remaining pecorino.