Preheat oven to 425˚. Toss cauliflower florets with 2 teaspoons olive oil. Spread onto a sheet tray roast until cauliflower is browning and tender, 25 to 30 minutes.
Cook pasta according to directions. Drain and place in a bowl.
In a sauce pan, heat the remaining two tablespoons of olive oil over medium-low heat. Add in the shallot and cook until translucent, 4 to 5 minutes. Stir in 1 cup of almond milk. In a separate bowl, combine the cold 2 tablespoons of almond milk with the cornstarch and stir until the cornstarch is dissolved. Pour into the pot with the shallots and whisk well. Continue to whisk (everything will blend together) until the mixture begins to thicken. Remove from heat and add in the lemon juice, zest, salt, and pepper.
Add the roasted cauliflower to the pasta and pour the sauce over, tossing until everything is well combined. This meal is best eaten hot as the noodles will soak in the sauce over time. Add a bit of pasta water to thin the sauce out if desired. Serve with toasted almond slices and chili flakes if desired.