1 large head cauliflower (about 2 pounds), trimmed and cut into 1-1/2-inch florets
1/4 cup olive oil
1 teaspoon kosher salt, plus more as needed
1/4 cup golden raisins, also known as sultanas, coarsely chopped
2 tablespoons sherry vinegar
2 tablespoons water
4 ounces French or Italian bread (about 1 [2-inch] slice), crust removed
2 medium garlic cloves, finely chopped
1/4 teaspoon red pepper flakes
2 tablespoons coarsely chopped fresh Italian parsley leaves
Heat the oven to 425F and arrange a rack in the middle. Place a baking sheet in the oven as it heats.
Place the cauliflower in a large bowl and drizzle it with 3 tablespoons of the oil. Add the measured salt and, using your hands, toss to coat. Remove the baking sheet from the oven and carefully spread the cauliflower on it in an even layer. Reserve the bowl for later (no need to wipe it out). Roast the cauliflower, stirring halfway through, until deeply browned in spots, about 25 minutes. Meanwhile, plump the raisins and make the breadcrumb mixture.
Place the raisins, vinegar, and water in a large frying pan and bring to a simmer over medium-high heat. Cook, stirring often, until the raisins are heated through and the liquid has almost all evaporated, about 5 minutes. Turn off the heat, remove the raisins to a small heatproof bowl, and set aside. Reserve the pan.
Using your hands, tear the bread into pieces about the size of raisins and place in the reserved large bowl (you should have about 1 1/4 cups); set aside.
Return the reserved frying pan to medium heat, add the remaining tablespoon of oil, and heat until shimmering. Add the breadcrumbs, season with salt, and stir to combine. Toast the breadcrumbs, stirring occasionally, until golden brown all over, about 8 to 10 minutes. Meanwhile, wipe out the bowl with paper towels and set it aside.
When the breadcrumbs are done, add the garlic and red pepper flakes to the pan, and stir to combine. Cook until fragrant, about 30 seconds. Remove the breadcrumb mixture to the reserved bowl. Add the roasted cauliflower, plumped raisins and any liquid, and parsley to the bowl and toss to combine.
Taste and season with salt as needed. Transfer to a serving platter and serve immediately.