Preheat the oven to 200°C (400°F)
Drizzle the potatoes with olive oil & season with salt & pepper. Toss to cover.
Transfer the potatoes to a sheet pan and roast for approximately 30 minutes, mixing the potatoes half way through.
Blanche the green beans in heavily salted water for 6 minutes
Strain and plunge in ice water to stop the cooking entirely. Transfer to a kitchen towel and let dry.
Wash and chop the lettuce into smaller, bite size pieces and add to a large, wide salad bowl lettuce leaves.
Drizzle 15ml (1tsbp) of vinaigrette over the lettuce and sprinkle with a bit of salt.
Toss the green beans with a bit of olive oil & season with salt & pepper.
Break up the canned tuna with a fork and season with salt & pepper.
Add all of the ingredients to the bowl, creating mounds of each ingredient then add the tuna to the center of the salad.
Drizzle the salad with some vinaigrette and serve the rest along side the salad.