Wash the cauliflower head and cut the stem and separate the florets. I mostly separate the florets using hands, occasionally using the knife as needed. If you are buying frozen or fresh cauliflower florets instead of the whole cauliflower head, you can skip this step.
Wash the florets lightly again and transfer the florets to a large bowl.
Add the lemon juice and salt, mix well to coat all the florets.
Add the black pepper and garlic powder, mix well.
Add the oil and mix everything well. Let the cauliflower sit there and get marinated for at least 15 minutes for best results.
Preheat the oven to 375 degree Fahrenheit.
Grease a large baking sheet with oil.
Transfer the cauliflower florets in a single layer in the baking sheet. If you have more florets left after arranging them in a single layer in the baking sheet, you can roast the remaining in a second batch. If you will be able to complete this in one or two batches will depend on the size of the cauliflower head used and also the size of your baking sheet.
Bake for 25 to 30 minutes for until the cauliflower florets have started to turn golden brown. Mine was done just after 25 minutes, but the heat in different ovens can vary so if you are roasting cauliflower florets for the first time in your oven, you have to watch this after about 25 minutes so as to avoid overdoing. Some ovens may take up to 30 minutes especially if you are doing the first batch.
Transfer the browned and crispy roasted cauliflower florets to the serving plate (as soon as you can handle the heat), serve and enjoy with rice or pasta (or anything you like) for lunch or dinner or snacks!