Pat the beef loin roast dry with paper towels.
In a small bowl, mix salt, black pepper, garlic powder, and onion powder.
Rub the seasoning mixture evenly over the entire beef loin roast.
Heat olive oil in a large skillet over medium-high heat.
Sear the beef loin roast on all sides until browned, about 2-3 minutes per side.
Place the sliced onion, minced garlic, carrots, and celery in the bottom of the crock pot.
Place the seared beef loin roast on top of the vegetables in the crock pot.
Pour beef broth and red wine over the beef and vegetables.
Add fresh rosemary, thyme, and bay leaf to the crock pot.
Cover and cook on low for 6 hours, or until the beef is tender and reaches an internal temperature of 135°F (for medium rare) to 145°F (for medium).
Remove the beef loin roast from the crock pot and let it rest for 10 minutes before slicing.
Discard the bay leaf and herb sprigs from the crock pot.
Serve the sliced beef loin with the cooked vegetables and spoon some of the cooking liquid over the top.