Preheat the oven to 400ºF. In a small bowl combine the smoked paprika, garlic powder, cayenne, salt, and some freshly cracked pepper.
Spread the frozen cauliflower florets out onto a baking sheet (no need to thaw first), then drizzle with olive oil and sprinkle the spices over top. Toss the cauliflower in the oil and spices until they are fairly evenly coated.
Transfer the seasoned cauliflower to the preheated oven and roast for 30 minutes, stirring once half way through.
About half way through the roasting time, begin the cheese sauce. Add the evaporated milk and butter to a small sauce pot. Heat over medium, while stirring, until the butter has melted and the evaporated milk is hot. This should only take a couple of minutes.
Turn the heat under the evaporated milk to LOW and begin whisking in the shredded cheddar, one handful at a time, making sure the cheese is fully melted before adding the next handful. Once all the cheese is melted into the evaporated milk the sauce will thicken. If it’s still very liquidy, keep the sauce over low heat and whisk constantly until it thickens. Often the cheese appears to be completely melted, but it has not yet totally emulsified. Remove the cheese sauce from the heat until ready to serve.*
Once the cauliflower has finished roasting, divide it into bowls or place it in a serving platter, then pour the cheese sauce over top. Serve immediately.