Chop the vegetables. Remove the outer leaves from the cauliflower, and chop off the chunky part of the stalk. Then separate the florets. I'd suggest that you also cut some of the florets through the stalk as it's best to have bite size pieces. Include some of the cauliflower leaves if you like. Cut the sweet potato into 2 cm squares, I leave the peel on. Add the olive oil, spices and seasoning to a large bowl. Add the chopped cauliflower and sweet potato, and stir to mix and coat the vegetables. You may want to do this in batches to make it easier.
Spread the vegetables out on a baking tray. If necessary, use 2 trays so that there is some space around the veggies for them to roast properly. I use a reusable baking sheet on the tray to make clean up easier, but it's not essential.
Roast in a preheated oven at 170 degrees for around 30-40 mins. The vegetables should be a rich golden colour and yield easily to the point of a knife.