In a large bowl, mix together the garlic, salt, olive oil, and balsamic vinegar. Toss the green beans to coat well.
Place in an even layer on a parchment-lined baking sheet and roast on 475ºF for 8-12 minutes or until they're getting slightly roasted, but before the garlic turns dark brown.
Notes
Double or triple this recipe to feed a crowd! UPDATE: I originally wrote 1 Tablespoon balsamic vinegar, but I recommend starting with 1 teaspoon instead. You can always add a little more when you serve them.