Make the vinaigrette: In a bowl, whisk together lemon juice, pink pepper, white pepper, and salt. Whisk in honey. Drizzle in olive oil in a slow stream to emulsify. This is a temporary emulsification and needs to be whisked just before serving.
In a heated pan with olive oil saute the potatoes. Season with salt and pepper. Cover the pan and roast until potatoes are tender. Add sun dried tomatoes to the pan. Transfer mixture to a bowl. With a hand-held masher, mash the mixture until fluffy. Check for seasoning. Place the potatoes mixture into a pastry bag fitted with a round tip.
To hydrate the rice paper wrappers, fill a large bowl with warm water. Place the wrappers in water for about 3 minutes until soft.
Remove one wrapper at a time from the water, lay out on a flat surface, and blot with a paper towel. Pipe a 5-inch strip of mashed potatoes in the center of the wrapper. Lay a tuna bar and a piece of scallion evenly next to the potato. Roll into a spring roll.
In a very hot pan with oil saute the spring rolls quickly, browning all sides. Cook on very high heat, making sure not to cook the tuna.
Cut each spring roll into 5 pieces. Brush with olive oil. Drizzle with the vinaigrette and serve immediately.