In a large skillet, cook and crumble ground beef with the onion over medium-high heat until beef is thoroughly cooked. Drain excess grease. Add sloppy joe seasoning mix, tomato sauce, fire roasted diced tomatoes, and roasted red bell peppers with the reserved juice. Stir to combine. Heat to boiling over medium-high heat. Add 12 oz uncooked rotini pasta; toss until pasta is submerged.