Preheat oven to 450°F and line a large sheet pan with parchment paper.
In a large bowl, combine olive oil, chili powder, cumin, paprika, cayenne, garlic powder, and salt to make a spice mixture.
Add sliced peppers and onions to the bowl, toss with half the spice mixture, and spread on the sheet pan.
Roast vegetables for 5 minutes while you prepare the shrimp.
Toss shrimp with remaining spice mixture and lime juice.
Remove pan from oven, add shrimp to the vegetables, and return to oven for 6-8 minutes until shrimp are pink and cooked through.
Serve immediately with warm tortillas and your favorite fajita toppings.