Preheat oven to 425 degrees F.
Remove outer leaves from the cauliflower. Cut it in half and cut out and discard the core. Cut the cauliflower into bite-sized pieces.
Toss the cauliflower in a large bowl with the olive oil to coat. Sprinkle on curry powder and salt and toss to coat.
Spread out in an even layer on a large rimmed baking sheet and transfer to the oven.
Roast the cauliflower until the bottom is beginning to brown, about 10 minutes. Turn over and continue roasting until tender, 5 to 7 minutes more. Return to the bowl and toss with lemon juice and cilantro.
