Heat oven to 425° F. On a rimmed baking sheet, toss the potatoes, garlic, oil, ¾ teaspoon salt, and ¼ teaspoon pepper.
Roast the potatoes, turning once, until golden brown and crisp, 30 to 35 minutes.
When the potatoes have 5 minutes left to cook, bring the wine to a boil in a large pot.
Add the mussels and simmer, covered, until they open, 3 to 4 minutes.
Mix the pesto into the cooking liquid. Serve with the oven fries.