Preheat the oven to 400 degrees F.
Drizzle the olive oil on top of the squash and season with salt and pepper. Roast the squash on a baking sheet skin-side up for 40 minutes. Let cool, then use a fork to pull out the strands of squash.
Whisk together the mayonnaise, vinegar, mustard, celery seed, Sriracha and sugar in a bowl. Mix the dressing and squash together and season with salt and pepper.
Serve on the side or on top of your favorite sandwich. I like it on hot pastrami on rye bread!