I don't know why you couldn't steam them, then cut them in half and roast them as usual.
I sometimes do this with fresh brussels sprouts because I like the finished texture.
I cut them in half, mix them with chopped garlic, olive oil, salt & pepper, and sometimes dried cranberries. Put them spread out on a cookie sheet, in a 350-ish oven for 10-15 minutes. Then flip them to their other side and roast for another 10-15 muntes until they are done to your liking.
Yumm!!