Heat the oven to 425°F. Toss tomatoes, red pepper, onion, jalapeno and garlic with olive oil and 1/2 teaspoon salt on a rimmed sheet pan. Roast for 25 to 30 minutes until softened with a few browned edges.
Blend roasted vegetables and their juices with cumin until smooth, venting the blender lid carefully for steam. Pour into a 5-quart slow cooker.
Season chicken with remaining salt and nestle the whole breasts in the salsa. Cover and cook on low for 2 1/2 to 4 hours, checking from 2 1/2 hours and removing each breast as it reaches 165°F.
Cover cooked chicken on a clean plate. Stir cream cheese into the hot salsa until completely melted, about 3 to 5 minutes, then add lime juice.
Return whole breasts to the sauce just long enough to coat them. Serve one per person with the creamy roasted salsa spooned over the top.