Would roasted red potatoes and roasted Brussels sprouts be good together?

I think they'd be fine! I like Mr. Vittles' idea a lot, but I would be concerned the vegetables would burn before the chicken is ready. I'd personally roast everything separately so I can achieve optimum crispiness/doneness for each.... and use the chicken drippings for gravy.

Yeah, I think they'd work just fine together. I'd make sure to cut the potatoes and sprouts about the same size, and I might parboil the potatoes.

They are delicious together, especially with a roasted chicken. If you have leftovers, a sunny side up egg on top would make a great breakfast. The frozen sprouts will roast up fine.

I think it would be good. But they may be ready at different rates, so cut the potatoes small or slice them. Brussel sprouts roast pretty quickly at high heat. No experience with frozen ones, though.

Consider using the two veggies, as your base for the chicken. That way, they will get coated in chicken schmaltz and fry up a bit in the oven. It is a slightly unconventional pairing of flavors, but it may yield tasty results.