Lay sheet pan next to your workspace. In a large bowl, toss onions and peppers in 2 teaspoons of oil until coated, then scatter in single later on baking sheet.
Place in oven to roast for 10 minutes.
Juice 1 and ½ of the limes into a blender.
Slice the remaining half lime into wedges to use for serving
Add garlic and remaining oil to blender. Then add salt and spices. Pulse once to combine.
In large ziplock back or medium bowl, pour mixture over shrimp and marinate for 15 minutes.
When peppers and onions are finished roasting, remove shrimp from marinade and space evenly on the baking sheet.
Roast the shrimp and veggies for 8 more minutes, or until shrimp are pink.
Serve over cauliflower rice, with a low-carb tortilla (Siete makes my favorite!) Add Greek yogurt, lime wedges, extra cilantro, or hot sauce!