Toss the cauliflower florets with olive oil and salt. Spread on a baking sheet and roast for 25-30 minutes until golden and tender.
While the cauliflower is roasting, make the Romesco sauce. In a blender, combine roasted red peppers, toasted almonds, garlic, red wine vinegar, olive oil, smoked paprika, and salt. Blend until smooth.
To assemble the sandwiches, spread a generous amount of Romesco sauce on the bottom half of each toasted bread roll. Top with roasted cauliflower and arugula. Place the top half of the bread roll on top.