Preheat oven to 425 degrees.
Toss cauliflower, 2 Tbsp. olive oil, and 1 tsp. salt on a rimmed baking sheet. Roast for 20 minutes until the bottom side is brown and crispy. Toss and roast the other side until brown and crispy, 15-20 minutes.
While cauliflower is roasting, prepare the couscous and dressing. Bring 1 cup of water to a boil (1.25 cup if using whole wheat couscous). Add 1/4 tsp. kosher salt and the couscous. Cover and remove from heat. Let sit for 5-10 minutes while couscous absorbs the water.
Combine the lime juice, garlic, 4 Tbsp. olive oil, 1/2 tsp. salt, and plenty of fresh black pepper to a large bowl.
Add couscous to the bowl and toss to coat in the dressing. Then add the cauliflower, radishes, currants (or raisins), and cilantro. Toss gently to combine. Taste and season with more salt if needed.
Serve warm or at room temperature. Salad will last 4-5 days covered in the refrigerator.