Place poblano and jalapeno on a foil-lined baking sheet. Place in the oven under the broiler. Turn occasionally until all sides are black and blistered.
Remove from oven and immediately place the peppers in a bowl and cover tightly with plastic wrap. Let steam for 10 minutes.
Remove peppers and gently scrape the blistered skin off using the sharp side of a knife. Cut the stems off and scrape away the seeds too. Dice remaining flesh and set aside.
In a non-stick skillet over medium-high heat, add olive oil, onion and peppers. Sauté until onions are softened and brown. Add garlic and cumin then cook for 1-2 more minutes. Remove skillet from heat.
To a slow cooker, add Velveeta, Rotel, and chile pepper mixture. Cook on low for 3-4 hours or on high for 1-2 hours. Stir occasionally. Serve with tortilla chips. Store leftovers in a lidded container in the refrigerator for up to 3 days.