1. Cut off pointed end of garlic; place garlic on a piece of aluminum foil, and drizzle with 1 Tbsp. oil. Fold foil to seal. Brush corn with remaining 1 Tbsp. oil, and place on a baking sheet.
2. Bake garlic at 400° for 1 hour. After 15 minutes, place corn in oven, and bake, with garlic, 45 more minutes or until corn is golden brown. Squeeze pulp from garlic cloves, and set aside. Let corn cool completely.
3. Hold 1 corn cob upright on a cutting board, and carefully cut downward, cutting kernels from cob. Repeat with remaining 2 corn cobs. Discard cobs. Set corn aside.
4. Cook potatoes in boiling water to cover in a large saucepan until fork-tender (about 15 to 20 minutes). Drain and return to pan.
5. Whisk together reserved roasted garlic pulp, sour cream, and next 6 ingredients in a medium saucepan over medium heat until butter melts and mixture is thoroughly heated.
6. Mash potatoes slightly; add warm milk mixture to pan, and continue to mash just until blended (mixture should be coarsely mashed). Stir in chopped cilantro and reserved corn.