I cut it and brush with olive oil, roast side up, and I've never had an issue where it gets tough. I cook it at 400 for about 45 mins, or until tender.

It depends, really, on how you are using it. If you want heavier caramelization but more moisture, roast it on a good, heavy dark baking sheet, cut side down. (I leave the seeds and fibers around them in, by the way, when roasting skin side down.) If moisture is an issue in your recipe or intended use, roast it skin side up. ;o)

Yes, cut side up. I first brush it with some butter and then add grated parmigiano before shoving it in the oven.

I have roasted cut side up with some broth in the hole, and basted now and again, that works pretty well!