Preheat oven to 425°F. Line a baking sheet with parchment paper and set aside.
Trim the tough, woody stem end from each green bean by cutting it off with a knife or snapping it off with your hands. Discard the trimmed ends. Place the prepared beans on the baking sheet.
Cut the strawberries in half and add them to the baking sheet. Add the chopped bell pepper pieces to the baking sheet.
In a small bowl, whisk together the oil and vinegar. Pour the mixture over the beans, peppers, and strawberries. Toss to coat everything evenly.
Roast until the green beans are crisp-tender, have some caramelized golden or brown spots, and are no longer raw or tough. The strawberries should be softened and juicy, with some edges possibly caramelized. The bell pepper pieces will be tender, with wrinkled skin and possible golden edges. This typically takes about 40 to 45 minutes—but start checking after 30 minutes to avoid burning.