It depends on the vegetable. I like to roast at a little higher temp than the first answer. I often use 450 degrees and toss with olive oil. skinny green veg like asparagus and green beans are quick cooking - maybe 10 to 15 minutes and I do toss them a little part way thru the cooking. Broccoli is pretty quick too, maybe 15 minutes. Cauliflower is more like 25 minutes. Hard squashes like butternut and sweet potatoes are like 30 minutes, usually. I think the best thing is to check them frequently.

Make sure the size of the cut is the same so they cook at the same speed. I prefer a higher temp, 400F, and toss in a bit of oil -and- some tomato paste to give a bit of flavor and help the caramelization process. Also, I put beets in a separate tin foil pouch (open top) so they do not bleed color into the other veg. Toss them in just before service. Sweet potato and yam also cook faster so add those at the halfway point.

It also depends on how large the vegetables are cut and how done you like your vegetables. I like mine a bit caramelized, so it takes closer to half an hour for mini-peppers, cubed sweet potatoes, cubed beets, and carrots.

Depending on the type of vegetable(s) you plan to roast, I suggest roasting the veggies for 20 minutes at 400 degrees. Don't forget to toss the vegetables at the halfway point in the cooking process.