Do not salt the aubergine first. A hot oven collapses it fast enough that there is nothing to draw out, and salting only means it sits about going soft before it ever sees heat.
Five minutes in the marinade is enough. Aubergine drinks oil, so a long soak does not season it, it just loads it. Toss, spread out, roast.
Watch the halloumi rather than the clock. It is ready when it has taken colour and given a little; left longer it tightens and goes squeaky and rubbery, and it will not come back.
Keep the offcuts. The trimmings from shaping the rounds grill in the same time and go on top, so nothing is wasted and the plate gets some crunch.