Heat the oven to 425°F. Line a baking sheet with parchment paper or a silicone baking mat, lining the pan isn't completely essential, but this helps with cleanup.
In a large bowl, then toss the cauliflower florets using all the oil, salt, chili powder, smoked paprika, onion powder, garlic powder, and cayenne pepper.
Add the seasoned florets into the baking sheet. Spread them out, facing as lots of the flatter borders down on the baking sheet so they brown well.
Roast till the edges are brown and crisp and the insides are tender for 20-35 minutes. After 20 minutes, then give the cauliflower a stir to promote even browning.
Serve tossed with the a squeeze of lime juice and scallions.