Potatoes, cauliflower, asparagus and onions infused with fajita and some other spices and roasted in the oven is perfect dish on its own if you want more veggies in your diet, or great side dish for meat or chicken entree.
Cooking time for this dish in will vary depending on size of potato and cauliflower pieces. Potato in general will take more time to cook than other vegetables, slice it in smaller pieces and check its readiness with a knife before turning the oven off.
I used virgin olive oil spray here, spraying is a way more convenient than just pouring, it also helps to cut amount of oil to necessary minimum. However pouring oil will work as well.