Heat oil in a large saucepan over medium. Add onions, cook stirring occasionally until golden, about 10 minutes. Add garlic, jalapeno, and cumin; cook 5 more minutes.
Add tomato paste, and cook, stirring, 1 minute. Add beans and 1 1/2 cups water; bring to a boil, reduce heat to medium, and simmer, stirring occasionally, until thickened, 10 to 12 minutes.
Add corn, cook to heat through, 2 to 3 minutes. Remove from heat; stir in scallions.
To make burritos:
Heat tortillas according to package instructions; fill with rice, bean mixture, and cheese.
Assemble: Mound 1/4 cup rice, 3/4 cup bean mixture, and 1/4 cup cheese on one side of tortilla. Fold sides, and hold them in. Starting from filled end, holding sides in as you work, tightly roll into a bundle. Place on a baking sheet, seam side down, and prepare remaining burritos.
Serve immediately, with salsa and sour cream if desired.