Heat the olive oil in your large skillet over medium heat. Add the diced onion and bell pepper, and cook for about 5 minutes until they turn soft and slightly golden. This step builds the flavor base for your entire filling, so don't rush past it.
Add both cans of refried beans directly into the skillet with the softened veggies. Stir everything together and let it heat through for a few minutes until the beans are warm and well combined with the onion and pepper. The mixture should look smooth and easy to spread.
While the beans finish warming, lightly coat your 9x13 baking dish with cooking spray. This little step keeps the rolled burritos from sticking once they bake, so you won't lose any cheesy filling to the pan.
Lay each tortilla flat on a clean surface and spoon the bean mixture evenly across the center, leaving about an inch of space around the edges. Sprinkle a bit of cheese over the beans, then roll each tortilla up snugly like a little package.
Place the rolled burritos seam-side down in your prepared baking dish so they hold their shape. Cover the dish with foil and bake at 350°F for about 10 minutes, just until everything is heated through and the cheese has melted inside.
Pull the dish out of the oven, sprinkle a little extra cheese on top of the warm burritos, and let it sit for a minute so it melts. Serve alongside sour cream and salsa so everyone can customize their own plate.