Preheat oven to 400°.
Toss cauliflower and squash with approximately 2 tablespoons olive oil to lightly coat. Spread in a single layer on a rimmed baking sheet. Roast 25–30 minutes, until soft. Season with salt and pepper and reserve.
Toss bread cubes with another 2 tablespoons olive oil and toast in oven, stirring occasionally, until crisp and golden, about 11 minutes. Transfer to a large bowl and let cool.
Heat 2 teaspoons olive oil in a small frying pan over medium heat. Add shallots and cook until golden brown, stirring occasionally. When shallots are soft and golden, transfer to bowl with bread.
Add cooked squash and cauliflower to bowl. Lightly toast pine nuts in a dry pan until flecked golden brown. Add to bowl along with capers, cranberries and arugula or spinach.
Whisk together red wine vinegar, herbs, salt and pepper, and whisk in remaining ½ cup olive oil until dressing is emulsified. Taste; adjust seasoning, and spoon over ingredients in the bowl, toss and allow flavors to meld for 10 minutes before serving.
Variation: Add pancetta to the salad. To make, thinly slice 12 ounces pancetta and cut into 1 ½-inch pieces. Heat a frying pan over medium heat. Add pancetta and cook, stirring occasionally, until pancetta is crisp. Remove with a slotted spoon and add to bowl with bread cubes. Add shallots to pan where the pancetta was cooked and proceed as directed above.