Roast squash or pumpkin is one of my favourite side dishes. I like it, in particular, with meat-heavy meals where I might otherwise have used potatoes and carrots (beef or lamb stews, roast pork or chicken, for example); it provides both heft and sweetness, and replacing two vegetables with one makes room for a bigger pile of seasonal greens.
But I also like squash in its own right, as something with a bit of texture to be served with creamy sides such as polenta, or beans and their broth. If you can find them, use winter squash like kabocha (delica), acorn or red kuri (onion). They’ve a particularly deep, nutty flavour, as well as being wonderfully sweet. Of course, the ubiquitous butternut squash is super-enjoyable too.
A final note: although rosemary has a reputation as a hardy herb, if you include it from the beginning of a roasting process, the leaves will burn, dry out and lose much of their flavour. Much better to add it towards the end to get the best from its aromatic oils.