What you write was generally correct many hundreds of years ago. Back then, you would find some Sephardi communities using rollers – there was no hard and fast minhag established yet. There are Torah scrolls extant from over 500 years ago in various museums and nearly all of them, whether sephardi or Ashkenazi, are on rollers.

Since the 1800’s, though, almost all Sephardi communities have used the boxes.

In the main synagogue in Algiers, according to the Algerian owner of this sefer, almost all of the sifrei Torah were in boxes. She acknowledged that many were unsewn from the boxes for transportation over-seas. I am certain that this scroll was once in a box because the rollers are clearly newer in make, and I can see the holes in the klaf where it was originally tied onto different mountings. Additionally, given the incredible weight of this sefer (50 lbs) it is extremely unlikely that it was originally intended to go onto rollers.

As far as Iraq goes- I don’t think Iraqi Torahs have been on rollers any time in recent history. I have the antiquities catalogs for the Hebrew University of Jerusalem and several other Jewish museums. They list and provide photos of Iraqi Torah scrolls going back to the first part of the 19th century and they are all in boxes. Incidentally, the Algerian Torahs in the catalogs are a mixed bag – most are in boxes, but a few re on rollers.