Q:

How to cook Brussells Sprouts and sweet potates in one oven? 

I need to roast the Brussels sprouts at 350 for 40" and bake the sweet potatoes at 425 for 60" in one oven.   How should I do it? 

A:

I have this problem frequently of needing to cook different things at the different temperatures in the oven at the same time.  I tend to get around it by choosing the average temperature of the two (in your case ~390F) and adjust my cooking times appropriately.  At 390F, I would cook for roughly the following times for your foods:
Brussels Sprouts    35"
Sweet Potatoes      70"
They should could in a pretty similar manner to your recipe, but I'd keep an eye on them to ensure they come out perfect. 
Hope that helps! 
Mike

