Preheat the oven to 450 degrees. Prepare an 8x8 glass baking dish by spraying with non-stick cooking spray. Cover a large cookie sheet with foil and spray with non-stick cooking spray {this will help the noodles not to stick to the foil}. Set aside.
Bring a large pot of salted water to a boil, and cook lasagna noodles until al dente. {Remember, they will be baked also and you don't want them to get too mushy.}
Meanwhile, in a small sauté pan, melt a tablespoon of butter and cook onion and thyme until softened and just beginning to turn golden.
Remove from heat and place sauteed onion in a medium bowl. Add ricotta, pumpkin puree, and egg, and salt, and mix together until well incorporated.
Ladle about half of the cheese sauce into prepared glass baking dish and spread out over the bottom.
When noodles are finished cooking, carefully remove from water and place each noodle on prepared baking sheet.
One at a time, scoop about 2 tablespoons {or more if you can fit it without overflow} of pumpkin/cheese mixture onto each noodle and spread evenly over length of noodle.
Roll each noodle up from the short end and place, seam side down, in baking dish with sauce. Repeat until all noodles are snugly in place.
Pour remaining cheese sauce over rolls. Sprinkle with extra grated cheese, and cover baking dish with foil.
Bake for about 20 minutes, until heated through and bubbly.
Remove from oven and uncover. Bake for another 5-8 minutes until the top begins to brown and the edges are bubbly and golden.