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.
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.