In a pot of boiling water, cook the lasagna according to the directions on the package until it is soft and pliable. Drain well and layout flat on a baking sheet.
Peel and cut potatoes into bite-sized chunks so they all cook evenly. Place in a pot with cold water over high heat. Once boiling, turn the heat down to a simmer.
Heat the oil in a non-stick pan on medium heat. Sauté the onion until golden brown (about 4-6 minutes), then set aside. In the same pan over medium heat, brown the ground beef breaking it up into smaller pieces until it is no longer pink. Season with salt and pepper, then set aisde.
In a saucepan, melt the butter. Once the butter is melted, stir in the cream to warm and then remove from the heat and set aside.
Check the potatoes by inserting a fork into them. Once the fork slides in and out with ease, remove from the heat and drain well.
Using an electric mixer or by hand with a whisk, whip the potatoes on low to break them up. Slowly add in the cream and butter mixture while whipping until smooth. Be careful not to over-whip or they will become gummy. Season with salt and pepper to taste.
Preheat the oven broiler on low.
Mix the mashed potatoes with sautéed onion, scallions, and 3/4 of the cheddar cheese.
Evenly distribute the potato mixture onto the lasagna. Spoon the ground beef on top and then roll up the lasagna noodles.
Lightly grease a baking dish with non-stick spray and place the rolled up noodles in. Top with the remaining cheese and place underneath the broiler to melt for about 3-5 minutes.
Garnish with scallions and serve with dinner rolls.