SQUASH: Preheat the oven to 425 degrees F. On a very large sheet pan (or 2 smaller ones), add the squash cubes, olive oil, dried thyme, and Italian seasoning. Season to taste (I add 1/2 teaspoon salt and 1/4 teaspoon pepper.) Generously space out the cubes on the sheet pan (if they're overlapping, they'll steam, not roast) and roast for 30-35 minutes, flipping every 10 minutes or until crisp tender. If they are too closely spaced or cut too large, they'll take 5-10 minutes longer. Remove and set aside.
PASTA: Set a strainer in the sink with a heat-safe mug or liquid measuring cup. Bring a large pot of water to a boil. Generously salt the water and then cook the pasta according to package instructions minus 1-1/2 minutes. Use the mug to remove a big scoop of pasta water and then drain the pasta and set it aside.
BACON: Meanwhile, dice the bacon and cook, over medium-high heat, in a large heavy-bottom skillet until golden and cooked to desired preference. Use a slotted spoon to remove the bacon onto a paper-towel-lined plate. Leave the drippings in the pan (if there is more than ~2 tablespoons grease, drain off the excess).
SHALLOTS/GARLIC: Reduce heat to medium. Add the butter to the skillet. Once melted, add shallots, garlic, and a tiny pinch of salt & pepper. Cook until golden, about 1-2 minutes. Pour in 1/2 cup of chicken broth; it should sizzle and boil. Scrape up any browned bits off the bottom of the pan. Once this 1/2 cup is mostly evaporated, add in the other 1/2 cup. Stir.
CREAM SAUCE: Add in the heavy cream and Parmesan cheese. Simmer, over medium heat, stirring occasionally for 3-5 minutes or until it thickens and slightly reduces.
TOSS: Add the spinach and pasta and use tongs to toss into the cream sauce until the sauce thickens, nicely coats the pasta, and the spinach cooks down (1-2 mins). If needed (sauce is too thick), slowly add in the reserved pasta water. Once sufficiently tossed, add in the roasted squash, 3/4ths of the bacon, and toss to coat.
SERVE: Serve immediately. Top individual plates with remaining bacon pieces, a touch more Parmesan if desired, and fresh thyme if using. Enjoy immediately! Pasta is best enjoyed right after being tossed!