Lasagna alfredo rolls! (Warning: this is a "add enough so it looks/tastes right" recipe, unless otherwise specified.)
First, make the filling: spinach, thawed and well drained; a good handful of chopped flat leaf parsley; ricotta (um, I think about 12 oz?); some of the cheese used in the alfredo; an egg; salt; garlic powder; nutmeg (not much, maybe 2-3 passes on the microplane). Last time I made this, I brunoise'd some shallots and sweated them in butter and put that in as well. That would be a nice thing to do, maybe some onions, some garlic. Whatever you're feeling.
(Actually, first should be turning the oven to 375F, getting a 9x11 baking dish ready - you could spritz with cooking spray, but I prefer making a parchment paper sling for easier cleanup - and getting your mise en place ready: squeeze some spinach, grate some cheese, chop some parsley, get a colander in the sink, etc.)
Then, get a pot of salted water boiling. Cook a box of lasagna noodles while you're making the alfredo. You don't even want them to al dente, just cooked enough that you can roll them up without them breaking.
Alfredo sauce: the way I remember is, a stick, a pint, a cup. That's a stick of butter, a pint of heavy cream, and a cup of Parmesan cheese. (I actually used Grana Padano for this, because Costco has it for a good price. It's tangier than Parm and I worried the kids wouldn't go for it but they did. I think it adds a nice bite to alfredo, which can get pretty heavy.) In a heavy saucier, melt the butter, then add the cream. Stir occasionally and bring just almost to a scald. Then whisk in the Parm slowly. Add salt, maybe some white pepper, little nutmeg (I skipped it here because I put nutmeg in the filling), garlic powder. If you haven't made alfredo before, be prepared to be surprised by how much salt it needs. Stir and taste and get it how you like it. Take maybe 2/3 c of the sauce and coat the bottom of the baking dish with it - just pour it in and shake the pan to get it spread around.
Okay, so you've got your pasta in the colander (it helps to have a sous-chef around, especially if he makes drinks). Rinse with cold water just until the noodles are cool enough to handle, shake dry. Take a noodle and scoop up a little filling with the other hand. I find it's easiest just to use my hands to get the filling patted and spread over the noodle - leave an inch or so uncovered at the end of the noodle. Roll up so that the uncovered end is on the outside of the roll (i.e. start rolling at the other end). Put that roll in the baking dish. Keep doing this 11 more times. If you're weirdly uptight like me, you could weigh your filling or divide it into 12ths to make sure you have the same amount for each roll.
Once you've got the rolls all made, pour the rest of the alfredo sauce over the top. Bake, uncovered, until you start seeing browned bits on the top of the pasta, 20-25 min. Pull the baking dish out and let it rest 5-10 min. I served mine finished with a sprinkle of parsley, Grana Padano cheese, black pepper, and rosemary finishing salt.