In a small bowl, combine kosher salt, black pepper, garlic powder, onion powder, and smoked paprika.
Rub the spice mixture evenly over the entire surface of the tri tip roast.
Heat olive oil in a large skillet over medium-high heat.
Sear the tri tip roast for 3-4 minutes on each side until browned; remove from heat.
Place sliced onions, minced garlic, carrots, and potatoes at the bottom of the crock pot.
Place the seared tri tip roast on top of the vegetables in the crock pot.
Pour beef broth over the roast and vegetables.
Add fresh rosemary sprigs on top.
Cover and cook on low for 6 hours, or until the roast is tender and reaches an internal temperature of 135°F (medium-rare) to 145°F (medium).
Remove the roast from the crock pot and let it rest for 10 minutes before slicing against the grain.
Serve the sliced tri tip roast with the cooked vegetables and pan juices.