Sombra Pumpkin: Is it known by other names?
Most winter squash is fairly interchangeable when cooking.
Obviously, there are differences in them (sweetness, density, size, flesh color), but if you're cutting it up and roasting it, then it's fairly universal (but you might need to cut up denser ones into smaller bits).
Tozer Seeds describes it as:

a combination of sweetness, flaky texture and depth of flavour

(Kings Seeds uses the exact same description)
I'm not sure what they mean by 'flaky', but it might mean that it can be treated like spaghetti squash, where the fibers are such that it can be cooked whole and then removed from the skin in long strands as a pasta substitute.
As it looks to be a smaller pumpkin, and they mention it's sweet, I'd recommend trying recipes for &quot;acorn squash&quot;.
And, if you roast it and it's not quite right ... then you can always mash it with other flavorings, or blend it with some stock to turn it into soup.