Prep the vegetables by peeling and chopping the carrots, parsnips, and onion into uniform 1-inch pieces.
Place the chopped vegetables and minced garlic into the bottom of the slow cooker.
Season the turkey breast on all sides with sea salt, black pepper, dried thyme, and dried rosemary.
Heat olive oil in a skillet over medium-high heat and sear the turkey breast for 2-3 minutes per side until golden brown.
Transfer the seared turkey to the slow cooker, placing it on top of the vegetables.
Pour the turkey bone broth over the ingredients, ensuring the vegetables are partially submerged.
Cover and cook on low for 5-6 hours or on high for 3 hours until the turkey reaches an internal temperature of 165°F.
Remove the turkey to rest for 10 minutes before slicing, then serve alongside the tender root vegetables and a drizzle of the cooking juices.