Preheat oven to 400 F.
While oven is preheating cook pancetta in a pan over medium heat about 4 minutes. Remove to plate or bowl lined with paper towel. Add diced Halloumi and saute for a couple minutes allowing to turn brown. Set aside.
Line a baking sheet with tin foil or parchment.
Add sprouts, pancetta, olive oil, and Halloumi on baking sheet. Sprinkle with salt and pepper and mix to combine. Spread into one layer on sheet.
Roast in oven for 20-30 minutes (depending on the size of your sprouts) tossing 1-2 times. If they are large you may need to roast a little longer.
Place in serving bowl and sprinkle with Tajin. Serve immediately.