Pat the roast dry, then season all sides with salt, pepper, and garlic powder.
Heat the olive oil in a heavy skillet over medium-high heat.
Sear the roast for 3–4 minutes per side until well browned.
Spread potatoes, carrots, and onions in the slow cooker.
Place the seared roast on top of the vegetables.
Sprinkle ranch seasoning and au jus mix evenly over the meat.
Add pepperoncini and pour in the pepperoncini brine.
Pour beef broth around the sides to avoid washing off seasonings.
Dot the top of the roast with butter pieces.
Cover and cook on Low for 8 hours, until fork-tender.
Shred the beef in the pot and toss with the cooking juices. Serve warm.