The proportions for this depends entirely on how many people you'll be feeding. If it's just my family, I'll do a small 11x7 pan. I was making dinner for two other families in addition to mine, so I filled a whole jelly roll sheet pan. Divide your vegetables into two categories - hard root types that need to cook a while and wimpier veggies that'll shrivel up and die if you leave them in the oven for an hour (bell peppers and asparagus).
I've found that I can get even the pickiest eaters to try things they haven't eaten before like parsnips and yams and they find them to be pleasant. So this is your chance. Pull out something new. Here are our favorites:
red skin potatoes
yukon gold potatoes
Preheat the oven to 425 while you prepare the vegetables by cutting them into roughly 1" chunks. Spray your pan with cooking spray. Pour all the "hard" veggies into a large bowl and drizzle olive oil all over them until they are all uniformly coated. Sprinkle a healthy dose of kosher salt and several grinds of pepper and toss again. Pour them out into the cooking pan and sprinkle your choice of either fresh or dried thyme and/or rosemary evenly over the top. Reserve the wimpy veggies and prepare them the same way, just don't add them to the pan until much later in the cooking process.
Roast for an hour (plus or minus a bit, depending on the size of your veggie chunks), stirring after 30 minutes, and then again 15 minutes later at which point you will add your wimpy vegetables and cook for another 15 or so minutes. They are done when the edges are crispy and caramelized (like the top picture) and they are fork tender.