Add all seasoning ingredients to small bowl. Whisk well to thoroughly incorporate, breaking up any clumps.
Place beef roast on flat surface. Pat all sides of beef roast with paper towels until completely dry, then thoroughly coat all sides of beef roast with seasoning mixture.
Add 2 tablespoons olive oil to large pot over medium-high heat. Once oil is hot and shimmering, place beef roast in pot. Sear 3 to 4 minutes, then flip and sear 3 to 4 minutes more. Repeat until all sides of beef roast are golden brown.
When beef is seared, pour in beef broth, orange juice, and lime juice. Cover pot with lid and cook over medium-high heat 2 to 2 ½ hours, until beef is tender and can be easily shredded with forks.
Transfer cooked beef roast to cutting board. Using 2 forks, shred beef roast completely.
Return shredded beef to pot. Reduce heat to low and cook, uncovered, 5 to 10 minutes or until liquid has reduced slightly.
While sauce reduces, warm tortillas in large skillet or in microwave layered between damp paper towels. Serve shredded beef in warmed tortillas with desired toppings.