Preheat your oven to 425°F (220°C). Line a sheet pan with parchment paper.
In a bowl, mix the olive oil with paprika, cumin, coriander, turmeric, garlic powder, salt, and pepper.
Rub the spice mix onto the chicken thighs until evenly coated.
Place the chicken on the sheet pan and roast for 20-25 minutes until fully cooked.
While hot, slice the chicken and assemble the sandwiches: place chicken on rolls, add sliced red onion, arugula, Havarti cheese, and sauce if using.
Return sandwiches to oven for 3-5 minutes to melt cheese if desired. Serve warm.