Should I boil red potatoes before roasting them?
In my opinion, it's a matter of how much time you have and what temperature your oven is set on already. I make these a lot, with a variety of dishes, so I've used multiple cooking methods. 

Ideal: They roast best, I think, being boiled just for a few minutes then roasted at 475 F for 30 minutes. 

Oven's already on low: If I have a more slow-cooking item already in the oven at 350 F, then I'll go ahead and put the potatoes in raw and leave them to roast for 60-90 minutes. 

Need them quickly: When in a time crunch, I've also had success boiling them until softened completely then broiling until browned (maybe 5-10 minutes).