Heat the oil in a medium-size pan over medium heat. Add the onion and sauté until lightly browned, 5 to 6 minutes; stir in the garlic and continue to cook until soft, 2 to 3 more minutes.
Stir in the tomato paste and sauté briefly. Add the roasted tomatoes, chipotles, and chicken stock; stir to blend and simmer for 10 to 15 minutes. Transfer to the jar o