In a large bowl or plastic bag, add pot roast to 12 oz Dr Pepper to marinate - at least 30 minutes, but up to overnight. Do not discard Dr Pepper marinade - we will add it to additional Dr Pepper to cook after browning pot roast.
After marinating, pat the chuck roast dry with paper towels. Season all sides generously with salt and black pepper.
Heat the olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat.
Sear the roast for 3–4 minutes per side until browned. Remove and set aside.
In the same pot, add onion and cook 3–4 minutes until softened.
Stir in garlic and cook another 30 seconds until fragrant.
Add tomato paste, cumin, smoked paprika, and oregano. Stir to coat.
Pour in beef broth, scraping up browned bits from the bottom.
Add Dr Pepper (from marinade + additional 12 ounces), adobo sauce, and chopped chipotle peppers. Stir well.
Return the seared beef to the pot.
Add potatoes and carrots to the pot.
Add bay leaves. Bring to a simmer.
Cover with lid and transfer to a 325°F (160°C) oven. Cook for 3–4 hours, until beef is fork-tender.
(Alternatively: simmer on stovetop low heat, or cook in a slow cooker on LOW for 8–9 hours.)
Remove bay leaves. Shred beef with two forks or a stand mixer, using the paddle attatchment.
Taste broth and adjust seasoning with more salt, pepper, or adobo sauce for extra heat/smokiness.
When potatoes and pot roast have been removed from dutch oven, bring liquid to a boil and then reduce to simmer until thickened for sauce. Spoon reduced sauce over potatoes and pot roast before serving.
Garnish with chopped fresh cilantro or parsley.